read the trilogy of books by Robert Monroe, founder of the Monroe Institute.
Journeys out of the Body
Far Journeys
Ultimate Journey
short answer… the psychic energy produced by ANY strong emotion, which is the literal food of the non-corporeal beings, who create universes as gardens in which to grow the "loosh" they feed on. the being you may refer to as God is one of that community of non-corporeal beings, and THIS universe is the garden He created. unpleasant truth… to God, you are a carrot, one of uncountably many carrots in the garden.