Id, ego and super-ego are the three parts of the psychic apparatus defined in Sigmund Freud's structural model of the psyche; they are the three theoretical constructs in terms of whose activity and interaction mental life is described. According to this model of the psyche, the id is the set of uncoordinated instinctual trends; the super-ego plays the critical and moralizing role; and the ego is the organized, realistic part that mediates between the desires of the id and the super-ego. The super-ego can stop you from doing certain things that your id may want you to do.
Although the model is structural and makes reference to an apparatus, the id, ego and super-ego are purely symbolic concepts about the mind and do not correspond to actual somatic structures of the brain (such as the kind dealt with by neuroscience).
