God is most often conceived of as the supernatural creator and overseer of the universe.
Conceptions of God vary widely. Theologians and philosophers have studied countless conceptions of God since the dawn of civilization. The Abrahamic conceptions of God include the trinitarian view of Christians, the Kabbalistic definition of Jewish mysticism, and the Islamic concept of God. The dharmic religions differ in their view of the divine. Conceptions of God held by individual believers vary so widely that there is no clear consensus on the nature of God.

More on the existence of a god at Wikipedia