Pantheism is the belief that divinity permeates the world or that God is everything, and everything is God; God is synonymous with the universe. Pantheism is a very naturalistic philosophy whose followers put emphasis on Nature and the Earth. God is usually understood as being a more abstract idea, instead of actually being an anthropomorphic deity.
Pantheism should not be confused with Panentheism which states that God exists and that every part of Nature is a part of God. In Panentheism, God is not synonymous with Nature. The best way to remember the difference is by remembering that in Pantheism Nature is God" but in Panentheism, "Nature is a part of God."