Sigmund Freud's psychoanalytic theory of personality divided the human psyche into three parts: the Id, the EGO, and the Superego. The Id is the unconscious part of the mind that contains basic instinctual drives and desires. The EGO is the conscious part of the mind that mediates between the Id and reality. The Superego is the moral part of the mind that develops from internalizing societal values and norms. In Freud's I, the Id is represented by the letters 'ICH', and the EGO is represented by the letters 'EGO'.