The Pure Creation
At the "top level" as it were ' the source of everything, is the limitless, utterly transcendent Paramshiva who is beyond all human comprehension and basically, unknowable.
Then there's Shiva as he is understood to manifest himself ' the Instrumental Cause of all creation and the one who sets in motion the five fundamental activities which give rise to the world ' Emission, Protection, Reabsorbtion, Concealment, and Grace. This form of Siva is held to have a "body" composed of mantras, which can be visualised, worshipped, and meditated upon.
Shiva-Tattva
Shiva-Tattva is sometimes conceived as the first "outward" movement of Paramshiva. It is sometimes described as the "static" aspect of universal consciousness ' the "support" and root of all things and potentialities in the world.
Shakti-Tattva
Shakti-Tattva is the "activity" of Shiva ' from Her the rest of the Tattvas arise. There is no real seperation between Shiva & Shakti. Shakti (at this level) is said to be "full of bliss" ' sometimes called AnandaShakti.
Will, Knowledge, Action
Related to Shiva-Shakti are the so-called "three corners" ' Icchashakti (primal power of Will ' also referred to as Sadashiva or Sadakhya), Gyanashakti (primal power of knowledge" ' also referred to as Ishvara) and Kriyashakti (primal power of action ' also referred to as Sadvidya)