The essence of the theory is that much seemingly random variation in behavior is actually quite orderly and consistent, being due to basic differences in the way individuals prefer to use their perception and judgment.
Perception involves all the ways of becoming aware of things, people, happenings, or ideas.
Judgment involves all the ways of coming to conclusions about what has been perceived. If people differ systematically in what they perceive and in how they reach conclusions, then it is only reasonable for them to differ correspondingly in their reactions, interests, values, motivations, skills, and interests. The MBTI is based on Jung's ideas about perception and judgment, and the attitudes in which these are used in different types of people. The aim of the MBTI is to identify, from self-report of easily recognized reactions, the basic preferences of people in regard to perception and judgment, so that the effects of each preference, singly and in combination, can be established by research and put to practical use. The MBTI functions as a tool that helps people in organizations to understand themselves and their behaviors.