Hinduism has given much freedom to people in worship. Hinduism says God has as many forms as there are trees, animals, etc. 

In fact, all of creation and everything in it is a part of God, so it seems to be polytheistic.  As the Gita says "The one who seems me everywhere and everything in me is wise."

But in reality Hinduism is monotheistic. As it says, it is only one god who has manifested and taken many forms like one body with many different parts. Each part plays its own role though it is part of one supreme being. All the little Gods in Hinduism are representations of one Supreme God.

In short, Hinduism is monotheistic, with one supreme being. One cannot really describe this supreme being because as it has no form, it is beyond time, space, and causation and cannot be speech. God is neither male of female, or is both and beyond.

Man has to see one in many and many in one, i.e. many forms supported by one who has taken many forms. All the waters come from one ocean, whether it is river, pond, or lake. Similarly God is like an ocean and the outlets are small manifestations