Freud used the iceberg is as an explanatory tool for his theory of the conscious and unconscious. In essence, Freud explained his theory through the use of the iceberg as a dominant metaphor.Freudian terms, the portion nearest the surface of the water -- personality -- is called the ego. Just below the ego, nearing the bottom, is the superego, the part of a person's interiority that offers moral or social restraint against the unknown, unauthorized impulses of the subconscious. Finally, the greatest portion of the hidden mass is the id, the darkest, most recessed province of human thought, motivation and desire.