What is the Hindu concept of God?

God is Brahman, the one, the changeless Truth and Reality. As Brahman cannot be conceived by the intellect, it cannot be defined; it can only be indicated. With respect to creation, God is the changeless substratum supporting the changing universe. Example; the god of waves is the ocean; the god of ornaments is gold; the god of pots is mud; the god of shirts is cotton. God is thus the cause and the effect. The effect is nothing but the cause in another form. And if the cause is removed, the effect ceases to exist.
Hinduism is refers to God as the Trinity of Brahma (the creator), Vishnu (the sustainer), and Shiva (the Destroyer). God is the supremely intelligent, ultimate cause from which the entire universe has emerged, in which the universe exists, and into which it eventually dissolves.
It is important to note that Hinduism is not polytheistic (belief in many gods, each a separate entity). Based on varying school of Hindu philosophy, Hinduism cab be called as monotheistic (belief in one God, manifesting different powers in different forms, where there is a dual relationship between God and the Individuals) or monist (belief in one God expressing as all forms, where God alone is or oneness alone is, and all of creation is but a manifestation of the one Reality).