Carl Gustav Jung (1875-1961) is best known as the founder of Analytic Psychology, also known as Jungian Psychology. This school of psychology shares similarities with Freud's psychoanalytic method in the emphasis it places on the role of the unconscious. However, Jung had other ideas about the unconscious.
Jung differentiates between the "personal unconscious," which he recognizes as an important part of the normal psyche, and the "collective unconscious", which refers to innate psychological predispositions shared by all human beings throughout history.
Jung also developed a theory of personality, which defines eight personality types based on the opposing attitudes of introversion and extroversion. According to him, attitudes refer to a predisposition to behave in a certain manner. People who are classified as introverts place importance on their subjective view of the world, while extroverts place more emphasis on objectivity and surrounding influences.
Jung further identified four functions of the personality: feeling, thinking, sensation, and intuition. Feeling and thinking refer to rational thought processes that allow us to understand the value and meaning of things. Sensation and intuition are non-rational functions by which we perceive the world - either through our sense organs (sensation), or by means of an unconscious process (intuition).
The four functions and the two attitudes combine to create eight distinct personality types: extroverted-thinking, introverted-thinking, extroverted-feeling, introverted-feeling, extroverted-sensing, introverted-sensing, extroverted-intuitive, and introverted-intuitive. These personality types formed the basis of the Myers-Briggs Type Indicator (MBTI), which is the world's most widely used personality assessment tool used to determine how a person perceives the world and makes decisions.