About the Myers-Briggs Type Indicator (MBTI) – Source: MBTI Manual ®
The essence of the MBTI-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 also reasonable to differ accordingly in their interests, reactions, values, motivations, etc.
The purpose of the MBTI instrument is to identify 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 into practical use.
The MBTI instrument contains four separate indices. Each index reflects one of four basic preferences which, under Jung's theory, direct the use of perception and judgment. The preferences affect not only what people attend to in any given situation, but also how they draw conclusions about what they perceive.
The E–I index is designed to reflect whether a person is an extravert or an introvert. Extraverts are oriented primarily toward the outer world; thus they tend to focus their perception and judgment on people and objects. Introverts are oriented primarily toward the inner world; thus they tend to focus their perception and judgment upon concepts and ideas.
The S–N index is designed to reflect a person's preference between two opposite ways of perceiving; one may rely primarily upon the process of sensing (S), which reports observable facts or happenings through one or more of the five senses; or one may rely upon the less obvious process of intuition (N), which reports meanings, relationships and/or possibilities that have been worked out beyond the reach of the conscious mind.
The T–F index is designed to reflect a person's preference between two contrasting ways of judgment. A person may rely primarily through thinking (T) to decide impersonally on the basis of logical consequences, or a person may rely primarily on feelings (F) to decide primarily on the basis of personal or social values.
Judgment – Perception (J-P)
The J–P index is designed to describe the process a person uses primarily in dealing with the outer world, that is, with the extraverted part of life. A person who prefers judgment (J) has reported a preference for using a judgment process (either thinking or feeling) for dealing with the outer world. A person who prefers perception (P) has reported a preference for using a perceptive process (either S or N) for dealing with the outer world.
4.Sixteen MBTI types
One pole of each of the four preferences is preferred over the other pole for each of the sixteen MBTI types. The preferences on each index are independent of preferences for the other three indices, so that the four indices yield sixteen possible combinations called "types," denoted by the four letters of the preferences (e.g., ESTJ, INFP).