In Myers and Briggs' theory , personality types are described in terms of four-letter codes, like ESTJ or INFP. Each of the four letters signifies a key aspect of an individual's personality.
Myers and Briggs' theory of personality types tells us that seemingly random variations in people’s behavior are actually quite predictable, as they are due to basic differences in the ways individuals approach key functions of thought, behavior, and interaction. Myers and Briggs described individual differences in terms of four personality dichotomies . Each dichotomy consists of two distinct and opposing styles, for instance Extraversion versus Introversion.
In order to determine your personality type, you first determine your preference on each of the four dichotomies:
Extraversion vs. Introversion
The Extraversion/Introversion dichotomy describes how a person gets their energy.
Introverts are energized by spending quiet time alone or with a small group. They tend to be more reserved and thoughtful.
Extraverts are energized by spending time with people and in busy, active surroundings. They tend to be more expressive and outspoken.
Sensing vs. Intuition
The Sensing/Intuition dichotomy describes how a person takes in information.
Sensors focus on their five senses and are interested in information they can directly see, hear, feel, and so on. They tend to be hands-on learners and are often described as "practical."
Intuitives focus on a more abstract level of thinking; they are more interested in theories, patterns, and explanations. They are often more concerned with the future than the present and are often described as "creative."
Thinking vs. Feeling
The Thinking/Feeling dichotomy describes how a person makes decisions.
Thinkers tend to make decisions with their heads; they are interested in finding the most logical, reasonable choice.
Feelers tend to make decisions with their hearts; they are interested in how a decision will affect people, and whether it fits in with their values.
Judging vs. Perceiving
The Judging/Perceiving dichotomy describes how a person organizes their world.
Judgers appreciate structure and order; they like things planned, and dislike last-minute changes.
Perceivers appreciate flexibility and spontaneity; they like to leave things open so they can change their minds.
Once you have determined which style you prefer for each of the four dichotomies, you can figure out your four-letter type code. In Myers and Briggs' system, the four letters of a personality type are the first initials of each of your prefererences. For example, someone with a preference for Extraversion, Intuition, Feeling and Judging would have the type “ENTJ.” A preference for Intuition is signified with the letter "N," to avoid confusion with Introversion.
There are sixteen possible combinations of preferences, making up 16 total personality types.
Note: Carl Jung introduced the “A” spelling of Extraversion into the scientific lexicon and it remains the psychologically accepted spelling.