The essence of Jung’s theory of types is that much of the seemingly random variation in behavior is due to basic differences in the way individuals orient themselves to the world and to themselves.

Jung believed that a personality type was defined by a preference for one function over others, and that each of these types was subject to two other fundamental functions, extraversion and introversion. Extraversion (E) and introversion (I), as defined by Jung, refer to a particular relationship between subject and object. The extraverted person will direct his or her attention primarily to the outer world of activity, of people, whereas the introverted person is more inclined to be detached from the external circumstance and focus attention on inner, subjective interests.