Can someone please explain what Carl Jung's theory was?
Jung's theory emphasized the importance of the unconscious
mind in relation to personality, like Freud.
On the nature of the unconscious, Jung said that "a storehouse of repressed memories are specific to the individual and our ancestral past." (Simply Psychology)
On the nature and purpose of sexual desire (libido), Jung said that "a generalized source of psychic energy motivating a range of behavior." (Simply Psychology)
He also said that cause of behavior comes from past experiences in future aspiration.
Those are three aspects of the theory. Hope that helped!