The word “Brahman,” or simply “Brahma,” is used in a generic sense to mean spirit. God, the individual souls, and the spiritual effulgence of God are all referred to as Brahman (its Sanskrit root means “the greatest”).
When the word is used in the context of Brahman, Paramatma, and Bhagavan—the three phases of the Absolute Truth—it refers to the impersonal effulgence of God (Bhagavan). Brahman is also called the brahma-jyoti, or “spiritual light.” It is fills the spiritual world and, when transformed by God, becomes the primordial elements of the material world. Thus it is said to pervade everything.