The Caretaker is a powerful psionic entity, perhaps a god, who watches over the Earth and guides its people. It is two-faced, composed of a feminine side called Gaia and a masculine side called Emmanuel. Gaia also symbolizes nature, emotion, and self-sacrifice, while Emmanuel represents scientific advancement and technological progress, logic, and enlightened self interest.
The Caretaker has only ever directly spoken to the Terrans twice, and only interfered directly in Terran affairs once (to stop World War IV from escalating further).