In Freud's theory of the mind, the psychical apparatus was differentiated into a number of systems of "agencies", each of which had distinct properties and functions, but which interacted dynamically and in conflict with each other.
Two of these agencies can be identified in Freud's writings.
First and Second Topography
The first theory, dating from about 1900 - the "first topography" - distinguishes between the unconscious, preconscious and conscious, while the "second topography", dating from 1923, differentiates the three agencies of id, ego, and super-ego (Das Es, Das Ich, Das Über-ich).
There is overlap between these two models, e.g., the ego and super-ego are partly preconscious and partly unconscious.