According to the tripartite model of the psychic apparatus in Freudian psychoanalytical theory, it is the deepest (i.e., true unconscious) component of the psyche. Hermetically sealed from the outside world, it is the instinctive desire to achieve one’s own aims that is governed by the pleasure-pain principle. Both the ego and the superego develop from the id and both are in constant conflict with it. Freud’s original use of the term derived from the German words das Es (the It), which were translated into English as id. He was at pains to point out that is was a metaphor designed to capture a system of action and behavior, something that appears to be neglected contemporary psychoanalytic writings.
See Anhedonia, Ego, Metaphor, Pleasure-pain principle, Psychodynamic theory, Psychoanalysis, Superego