The Myers-Briggs Type indicator was originally derived by Katharine Briggs and her daughter Isabel Briggs Myers. In turn, they used Carl Jung’s writings in the 1921 book Psychological Types.
These days, it is used to determine what kind of psychological preferences someone has. It was originally used to determine what types of jobs women in World War II could do best and most comfortably, but this was later rebuffed and now it is used only as an indicator for personality.
There are 16 types, denominated by a combination of four letters:
Extraversion (E) or Introversion (I), Sensing (S) or Intuition (N), Thinking (T) or Feeling (F), and Judgement (J) or Perception (P).
Every person is dominant on one side of the four scales and the combination of dominant traits then determines the personality type.
Extraversion or Introversion
People who lean to extraversion focuses on the outside world; things, people, actions. Those who lean to introversion channels their focus inward, reflecting, ideas and beliefs.
Sensing or Intuition
Those with dominance in sensing prefer to deal with facts, details and things that are certain; they trust information gotten from their 5 senses. Those who lean toward intuition like to add meaning to information and find things that aren’t obvious; they listen to their inner voice and trust insight.
Thinking or Feeling
Those who prefer thinking make decisions by using objective logic and an analytical approach, while those who prefer feeling look to their values, the needs of themselves and the other people and beliefs.
Judgement or Perception
Those who prefer judgement want their lives to be stable and decided while those who prefer perception want flexibility and new options.
Each in combination forms a unique personality type. A free test is available here.
I find it useful to divide my characters into personality types if I struggle to differentiate between them. I use it as a base to work from, giving me a clearer image of who this person is.