According to Vedas there are three things that are eternal: God, the Soul and Prakriti (physical matter in the subatomic state) (Rig Veda 1: 164: 20, 22 and 44, 10: 82: 7, Yajur Veda 40: 1, 40: 15, Atharva Veda 4: 35: 1, 10: 8: 2-4, Shvetashvatra Upanishad 1: 10).
God is the agentive cause for the creation of the universe, prakriti is the material cause of universe, and souls are the consumers for whose benefit the universe is created.
God is the Creator, the Supreme Spirit or Consciousness, and the Eternal Bliss. On the other hand prakriti, while eternal, by itself is inert. Though, the soul is eternal and conscious (aware), it usually lacks bliss.
The soul has a choice, it can aim towards reaching God—the Eternal Truth, the Supreme Consciousness and the Supreme Bliss and it-self acquire bliss, or it can be lost in the distractions of prakriti (universe) and remain unfulfilled and lacking in joy.
The description of God, soul and prakriti may be summarized as follows:
God is Sat-Chit-Änand (Sachidänand):
Sat = Eternally Exists, Eternal Truth
Chit = Supreme Consciousness
Änand = Supreme Bliss
Soul is Sat-Chit:
Sat = Eternally Exists
Chit = Conscious, aware
Prakriti is only Sat
Please note that this belief in three eternals is based on the Vedas and Upanishads is also called Traitvad (three eternals) and in many ways is quite different than the commonly held views of the Hindu Religion based upon the Purana’s and/or Vedanta’s advaita—monism beliefs which state that Brahman—God and jiva—the soul are identical and prakriti the physical matter is maya—an illusion.