What is Visnu-sakti-tattva?

Srila Prabhupada explains the meaning of Visnu-sakti-tattva-

Srila Prabhupada - "Tattva is manifested in different ways: Visnu-tattva, Viṣṇu-śakti-tattva, jīva-tattva, like that." (Lecture SB, Canto 6 Ch 2 text 7, Vrndavana, Sep 10, 1975) 

1 - Viṣṇu-tattva, (Balarama,  Visnu, Narayana, Maha-Visnu, Garbhodakashayi Visnu etc.

2 - Viṣṇu-śakti-tattva, Srimati Radharani and Here unlimited associates know as the internal potency

3 - jīva-tattva, the individual jiva-souls who experience a independent existence from Krsna, and have their own individual identity, personality, character,  desires and free will separate from Krsna's Personality.

There is also another sakti energy of Krsna who is in a league of his own and that is Siva-tattva (Lord Siva).

Śakti-tattva means the energy of God and refers to many different categories of living entities. 

However, when putting Viṣṇu in front of sakti, like Visnu-"sakti"-tattva, it then refers to the direct expansions of Krsna  whereas sakti can also refer to the individual jiva-souls.

Krsna has many different energies called sakti. The jiva-souls are one, Matter is one, the consort expansions like Srimati Radharani are one.

Srila Prabhupada - "Sakti or shakti means the "energy of Krsna." (SB, Canto 4 Ch 6 text 43, Purport)

The individual marginal living entities (jiva-souls) are parts and parcels of Krsna and are also the sakti energy of Krsna, along with other categories of living entities known as Viṣṇu-tattva and Visnu-"sakti"-tattva expansions mentioned above.

However, the jiva-souls are NOT on the same level as Krsna's direct expansions known as Viṣṇu-tattva and Visnu-sakti-tattva. 

Visnu-"sakti"-tattva is represented by Srimati Radharani or Krsna's internal potency.

"Sakti" as Visnu-"sakti"-tattva individuals refers to Krsna's direct expansions within His internal potency.^^.