Krsna is likened to the original candle that lights all the other candles of the same luminosity.

Srila Prabhupada - "In Brahma-saṁhitā the example is given of an original candle which lights a second candle. Although both candles are of equal power, one is accepted as the original, and the other is said to be kindled from the original. The Viṣṇu expansion is like the second candle. He is as powerful as Kṛṣṇa, but the original Viṣṇu is Kṛṣṇa. Brahmā and Lord Śiva are obedient servants of the Supreme Lord, and the Supreme Lord as Viṣṇu is an expansion of Kṛṣṇa."(Teachings of Lord Caitanya, Ch 8)

Furthermore, Krsna as His original two-armed Form, has 64 qualities and 4 of those are unique to only Him all the time because no Visnu-tattva expansion has those 4 extra qualities all the time like Kṛṣṇa  does.

They are as follows-

(1) Krsna is the performer of wonderful varieties of pastimes (especially His childhood pastimes)

(2) Krsna is surrounded by devotees endowed with wonderful love of Godhead.

(3) Krsna can attract all marginal living entities (eternal individual jiva-souls) all over the universes by playing on His flute.

(4) Krsna has a wonderful excellence of beauty which can not be rivalled anywhere in the creation, not even by His Visnu expansions who are known by unlimited names.

These four qualities out of Krsna's 64 attributes are important to understand because, as said, not even Visnu/Narayana forms of God have them all the time, only sometimes exhibited partially when Krsna expands Himself and appears in the material world.

Krsna the Supreme Personality of Godhead and cause of all causes expands into four basic categories of living entities, of those living entities, the ones who are almost equal to Krsna are called Visnu-tattva.

Other living entities like jiva-tattva (jiva-souls) are separated meaning they are more independent from Krsna with each individual jiva-soul having their own personality and character separate from Krsna's Personality. 

Another living entity, Siva-tattva (Lord Siva), is neither Visnu-tattva or jiva-tattva (jiva-soul) but is in a unique league of his own.

Srila Prabhupada - "Lord Śiva is not one of the living entities (Siva is NOT a jiva-tattva (jiva-soul) or Visnu-tattva (Krsna's direct expansion). Siva is in a league of his own, although he is simultaneously more or less, Kṛṣṇa Himself also (a paradox). 

The example of milk and yogurt is often given in this regard, yogurt is a preparation of milk, but still yogurt cannot be used as milk. Lord Śiva is an expansion of Kṛṣṇa, but he cannot act as Kṛṣṇa, nor can we derive the spiritual restoration from Lord Śiva that we derive from Kṛṣṇa. 

Lord Siva is simultaneously one with and different from the viṣṇu-tattva. Due to Siva's association with māyā, he is different from the viṣṇu-tattva, but at the same time he is an expansion of Kṛṣṇa's personal form. This situation is called 

bhedābheda-tattva or acintya-bhedābheda-tattva, which means- 

"Simultaneously one and different."

The essential difference between Siva and Krsna and Viṣṇu is that Lord Śiva has a connection with material nature, but Viṣṇu or Lord Kṛṣṇa has nothing to do with material nature."(From The Teachings of Lord Caitanya, Ch 8 and CC Madhya 20.308, Purport)

All are Krsna's expansions each having a portion of Krsna's 64 qualities however, only Kṛṣṇa has all 64 qualities in full.

Being all-powerful Krsna can expand Himself into forms with the same power and characteristics He possesses, without diminishing Himself in anyway.

Krsna is likened to the original candle that lights other candles of the same luminosity.

Krsna in His original Form has 64 qualities, 4 of those are unique to only Him all the time because no other Visnu-tattva expansion can manifest those 4 extra qualities all the time.

Krsna expands Himself to enjoy in a variety of ways through relationships with His innumerable devotees.

Some of His Visnu-tattva expansions like Maha-Visnu and Garbhodakashayi Visnu manage the decaying impermanent material creation (mahat-tattva), while other Visnu-tattvas manage their eternal blissful Vaikuntha planet (And they are unlimited)

The eternal individual jiva-souls can voluntarily choose to remain in the "anti-material" eternally youthful aspect of Spiritual Sky that that takes up 75%, or enter the temporary "material" impermanent decaying world which is 25% of the Spiritual Sky.

This is possible because the eternal individual jiva-souls have the eternal quality of free will as part of their spiritual constitution.

Visnu-tattva expansions (Visnu/Narayana) on the Vaikuntha planets are known by their trillions different names.

On the Vaikuntha planets, the relationship the eternal individual jiva-souls have with Lord Visnu is all in-reverence.

The jiva-souls there see Lord Visnu as the all powerful God and controller of everything and have a feeling of complete reverence with an attitude of deep respect and an overwhelming mood of awe and dedication in their loving devotion relationship and service to Visnu (God)

As said above, each Lord Viṣṇu on their spiritual planet has a different name based on the pastimes going on in their Vaikuntha planet.

The eternal individual jiva-souls in Goloka Vrindavana on the other hand, never see Krsna as God or even care, the jiva-souls (marginal living entities) in all the Vaikuntha planets always see Visnu/Narayana as the all worshipable Supreme Personality of Godhead and cause of ALL causes. 

However, Krsna in His original form in Vṛndāvana is only seen as a wonderful dear friend by all the enhabidents there and never ad God, not even by His parents or family members.

Krsna remains aloof from the affairs of the material temporary decaying creation and the perpetual all-in-reverence Vaikuntha planets.

This is because He is for ever enjoying loving pastimes with His friends, family, boy friends, girl friends and all other associates in Goloka-Vrindavana who Krsna sees are all equal to Him, even though all individual jiva-souls there see Him as the most amazing, caring, selfless Person they know, and love Him dearly. 

Amazingly, no one in Goloka-Vrindavana sees Krsna as God the Supreme controller of all, He is just their wonderful best friend, parent, lover etc.

Krsna’s first expansion is Balarama, His elder brother in Goloka-Vrindavan. From Balarama comes all other Visnu-tattva expansions.

Although Krsna expands into many forms identical to Himself, He remains the one individual original independent entity who is simultaneously one and different with His spiritual worlds and material creation.

Krsna eventually expands as Maha-Visnu (Karanodakshayi Visnu) and creates the material world which are actually the dreams of Maha-Visnu.

The material bodily vessels the eternal individual jiva-souls occupy in the material world, are chosen from Maha-Visnu's dreams because the entire material creation ARE the dreams of Maha Visnu according to Srimad Bhagavatam.

Srila Prabhupada – "This material creation is the spirit soul’s dream. Actually all existence in the material world is a dream of Maha-Visnu, as the Brahma-Samhita describes-

“This material world is created by the dreaming of Maha-Visnu. The real, factual platform is the spiritual world, but when the spirit soul wants to imitate the Supreme Personality of Godhead, he is put into this dreamland of material creation." (SB, Canto 4 Ch 29 Text 83)

This material creation is the eternal individual jiva-soul’s dream. Actually all existence in the material world is a dream of Maha-Visnu.

Srila Prabhupada – "Everything happening within time, which consists of past, present and future, is merely a dream. This is the secret in understanding in all the Vedic literature.” (SB, Canto 4 Ch 29 Text 2b)

Srila Prabhupada – “Our contact with matter is just like dream. Actually we are not fallen. Therefore, because we are not fallen, at any moment we can revive our Krsna consciousness, we break the dream." (SB, Canto 2 Ch 9 Text 1 Tokyo Japan 1972)

Srila Prabhupada – "Factually all of material existence is only a dream. Thus there is no question of past, present or future. Persons who are addicted to karma-kanda-vicara, which means ‘working for future happiness through fruitive activities’, are also dreaming. Similarly, past happiness and present happiness are merely dreams." (SB, Canto 4 Ch 29 Text 2b)

Maha-Visnu is laying down sleeping and in that sleep, He dreams the entire material creation.

Everything past, present and future is eternally their in His dreams, and those individual jiva-souls who choose to enter His material creation, live there in a material bodily vessel that all come from Maha-Visnu's dreams that are simultaneously the jiva-soul's desires (dreams) too.

Everything conceivable (imaginabl) are in the dreams of Maha-Visnu who can for fill any desire the eternal individual jiva-souls have. 

All material bodily vessels must be "hired" from Maha-Visnu to enter the material world.

Only the material bodily vessels or costumes and paraphernalia the visiting eternal individual jiva-souls have in the material world come from Maha-Visnu, but NOT the eternal individual jiva-souls (marginal living entities), they do NOT originate from Maha-Visnu or the impersonal brahmajyoti, they come (fall) from Vaikuntha or Goloka-Vrindavana (the active spiritual world)

The material bodily vessels are "hired" from the dreams of Maha-Visnu by the individual jiva-souls so they can enter His material creation in a suitable material bodily container or vessel that matches their desires that are independent from serving Krsna.  

Srila Prabhupada - "We are not the owner of this material body, not the owner of the material senses. The senses are "hired" from the Supreme Lord. This is very subtle understanding; one should know the proprietor of the senses is God." (March 1966, New York City)

All the material bodily vessels in the material world belong to Maha-Visnu and must be aquired from Him in order to enter the material world.

However, all such material bodily vessels are temporary and subject to constant decline, decay and always in need of constant maintenance, nothing made of matter lasts forever in the material world, everything is always in a constant state of decomposition.

This causes the eternal individual jiva-souls within those material bodies, who are visiting from the spiritual worlds as passengers in those bodily vessels, to continue taking birth after birth in the material world and continue trying to satisfy their desires and material senses.

The individual jiva-souls, who eternally have their own personality separate from Krsna's Personality, can "choose" to "voluntarily" serve Krsna in an unlimited variety of ways, or reject Him and enter the material world.

The individual jiva-souls are an eternal spiritual bodily form who have always originally looked like Krsna as their "original" spiritual bodily form - two-arms, two legs, etc in the spiritual world, and have their own unique personality separate from the Krsna's Personality.

Although in the spiritual world the eternal individual jiva-souls can voluntarily change their form to what ever they like to serve Krsna, from human form, to a blade of grass, to a pebble on the road, to a cow, a monkey, a gopī (cow herd girl) or gopa (cow herd boy) etc, there are unlimited forms because EVERYTHING in the spiritual world IS individual life forms.

In the material world (Maha-tattva) Maha-Visnu's dreams create the material universes known as Brahmanda universes including all material bodily vessels, which is 25% of the Spiritual Sky (also called the Brahmajyoti).

Within that 25% of the Spiritual Sky we find those billions of individual independent massive single universes called "Brahmandas." 

And deep inside each Brahmanda material universe, Maha-Visnu expands into a "secondary material universe" where Garbhodakashayi Visnu, Brahma and many planetary systems exist.

So, from Garbhodakashayi Visnu, Lord Brahma appears in each inner secondary material universe and builds the many planetary systems in his universe, there are billions of Garbhodakashayi Visnus and billions of Lord Brahmas but only one Maha-Visnu.

The size of each planetary system that exists in each material universe inside their Brahmanda, vary in size, some larger, some smaller than others.

In our material universe that is deep inside our surrounding Brahmanda, we have 14 planetary systems, and is considered a small universe.

Other universes inside their Brahmanda, have many more planetary systems.

The size of each Brahmanda and their inner universe depends on the how many heads Lord Brahma has.

Some Lord Brahmas, like ours, has only 4 heads, while other Brahma's within their material universe inside their Brahmanda, may have 10, 20, 50, 500, 1000, 100,000 or even a million or more heads.

All inconceivable to the mundane mind.

All the billions of Brahmanda universes coming from the Body of the sleeping Maha-Visnu (as seen in painting below) have a secondary inner universe deep inside them.

This means each of the billions of Brahmanda universes has their own Garbhodakashayi Visnu and Lord Brahma deep inside each Brahmanda where a secondary material universe exists.

Who is Radharani and Krsna eternally in their abode of Goloka Vrindavana?

Consequently, when Krsna wants to enjoy, He expands the potency or energy within Himself that gives him enjoyment. 

This potency is a person, Her name is Srimati Radharani.

Radharani is not a different person from Krsna, or, rather, she is both one with and different from Him. How could two people be one person or one person be two?

A simple example will illustrate how this is so. The sun cannot exist without the sunshine, nor the sunshine without the sun. We say, "the sun is in my room"—even though the sun itself is ninety-three million miles away—because the sun appears in the form of its energy.

Therefore the energy (the sunshine) and the energetic (the sun) are simultaneously one and different. 

Similarly, Radha and Krsna are simultaneously one and different. Krsna, the self-effulgent Lord, is the Supreme Personality of Godhead, and Srimati Radharani is His supreme pleasure energy.

Together They constitute the complete Absolute Truth. So, who is qualified to understand all discussed here?

One cannot understand anything about Radha and Krsna through mental speculation.

Krsna and His potencies are achintya, inconceivable, and ananta, unlimited. He is the very source of the mind itself, and therefore He is beyond the mind.

The limited mind cannot understand the unlimited Personality of Godhead. 

The Vedic literature explains this very logically- 

"That which is transcendental to material nature is inconceivable, whereas speculative arguments are all mundane. Since mundane arguments cannot touch transcendental subject matters, one should not try to understand transcendental subjects through mundane arguments."

When ordinary mundane intellectuals try to explain or interpret the identity or pastimes of Radha and Krsna, Krsna's unlimited nature bewilders them, and therefore they misconstrue everything.

Thus they sometimes consider Radha and Krsna to be like an ordinary boy and girl of the material world. But although they often pose as scholars, they do not know what they are talking about.

One should therefore strictly avoid the confused mundane ideas of such blundering intellectuals. If one wishes to understand Radha and Krsna, one must understand Them by hearing submissively from a bona fide authority. 

The original authority on Krsna is Krsna Himself. Everyone is first an authority regarding his own self, and this is also true regarding Krsna.

Moreover, since Krsna is unlimited, no one else can understand Him fully. Krsna's disciple Arjuna confirms this as follows in Bhagavad-Gita As It Is-

svayam evatmanatmanam

vettha tvam purusottama

bhuta-bhavana bhutesa

deva-deva jagat pate

Bhagavad-Gita As It Is - "Indeed, You alone know Yourself by Your own potencies, O origin of all, Lord of all beings, God of gods, O Supreme Person, Lord of the universe!" (BG, 10.15)

Although Krsna is inconceivable to mental speculation, those to whom He reveals Himself can understand Him. Krsna first gave such transcendental knowledge to Brahma, the first created living being.

Brahma later transmitted this knowledge to his son Narada, who transmitted it to Vyasa, the author of Bhagavad Gita As It Is. 

In this way, the knowledge has descended from master to disciple, through a chain of the Bhakti tradition, even down to the present day.

A spiritual master in this disciplic line is a bona fide authority regarding Krsna. He is the proper person from whom to receive transcendental knowledge.

What pleases Krsna?

According to Srila Prabhupada, Krsna is the reservoir of all pleasure, and therefore He is all-attractive. Yet Krsna Himself derives pleasure from the service rendered by His devotees.

Such devotional service attracts even Him. Krsna Himself, while speaking to a friend, confirms this-

Srimad Bhagavatam - "Lord Krsna said, My dear Uddhava, you may know from Me that the attraction I feel for devotional service rendered by My devotees is not to be equaled even if one performs mystic yoga, philosophical speculation or ritualistic sacrifices, studies Vedanta, practices severe austerities or gives up everything in charity. These are, of course, very nice activities, but they are not as attractive to Me as the transcendental loving service rendered by My devotees." (SB, Canto 11 Ch 12 Text 1)

Krsna is full in six opulence's- 

beauty, 

wealth, 

fame, 

strength, 

knowledge,  

renunciation. 

No amount of material opulence, therefore, can attract Him. Just as one could not attract a millionaire by offering him a few dollars, one cannot attract Krsna merely by one's limited material opulence. 

Nevertheless, pure devotional service attracts even Krsna. This is the unique transcendental excellence of devotional service.

Srimati Radharani is the embodiment of pure devotional service. No one can be a greater devotee than She. The very name Radharani comes from the Sanskrit word aradhana, which means worship. Her name is Radharani because She excels all in worshiping Krsna.

Although Krsna is so beautiful that He can attract millions of Cupids and is therefore called Madana-mohana, "the attractor of Cupid," Radharani can attract even Krsna. She is therefore called Madana-mohana-mohini—"the attractor of the attractor of Cupid."

The same Krsna who is not attracted by any amount of material opulence finds Srimati Radharani irresistible. 

One time Krsna, to joke with the gopis, the cowherd girls of Vrndavana, was hiding Himself beneath a bush, but finally they spotted Him from a distance. 

Krsna then changed Himself into His four-armed form of Narayana.

When the gopis approached and found Narayana instead of Kṛṣṇa, they were not very interested in Him; only Krsna's original two-armed form attracted them.

They therefore offered their respectful obeisance's unto Lord Narayana and prayed that He would bestow upon them the benediction of Krsna's eternal association. Then they went on searching for Krsna.

When Srimati Radharani passed by, however, Krsna tried to maintain His disguise as Narayana but was unable to do so; he kept slipping back into His original two-armed form. This illustrates the great influence of Srimati Radharani's pure transcendental love.

Krsna says in Bhagavad Gita As It Is that - "As one surrenders unto Me, He reciprocates and rewards them accordingly." 

Therefore the more Radharani tries to please Krsna, the more He desires to please Her, thus in turn increasing Her enthusiasm to increase His pleasure.

Therefore although the Lord is unlimited, both He Himself and His pleasure potency are always increasing. 

The all-blissful reciprocation between the Lord and His pleasure potency is expressed in the transcendental pastimes of Radha and Krsna, which are described in detail in "KRSNA, the Supreme Personality of Godhead Book" by His Divine Grace A.C. Bhaktivedanta Swami Prabhupada.

The reciprocation of loving exchanges between Radha and Krsna and all the eternal individual marginal living entities (jiva-souls) is the essence of spiritual love.

In the spiritual world, love between Krsna, and also among all His pure devotees, is based on selfless loving exchanges of service, reciprocation and personal offerings to Krsna that are unique to each individual devotee.

Such loving co-operation and selfless devotion among devotees, brings out the very best and full potential of each devotee's spiritual personality and character.

In this way, the pure devotees are always trying to please beautiful Krsna in so many ways in service and in playful sport in the mood of Krsna Consciousness.

And Krsna is so kind He always reciprocates in so many amazing ways.

However, all the pure devotees serve Krsna selflessly and unconditionally in their own unique way but in the mood of loving co-operation without any desire for personal gain.

Srila Prabhupada - "Love is reciprocal, voluntary, good exchange of feeling. Then there is love. Not by force! Krsna does not want to become a lover like that, ‘You love me, otherwise I shall kill you!" (Washington D.C. July 8, 1976)

Srila Prabhupada - "Because you are Son of God you have acquired the quality of your father. You have got little independence. So God does not interfere with your little independence. If you persist to go off and enjoy independently then God says, "All right, you can go." (Melb, Australia June 25, 1974)×=×