One of the most significant concepts to emerge from Jungian psychology--at least as useful as "introvert" and "extrovert"--is that of the "shadow." An individual's shadow is an unconscious region of the psyche formed by the conscious contents of the ego. So what you know about yourself casts a shadow composed of thing you don't know or don't want to know--the negative or dark parts. It is desirable that you become conscious of your shadow for two reasons: one, you can't work on parts of yourself you are not aware of and two, the parts of yourself you are not aware of can exert a force on your thoughts and behavior you cannot directly control.
Read next
From @wachter