Throughout history people have developed systems and categories in order to understand one another and to help explain the obvious similarities and differences between people. The ancient Greeks had a four part system by which they characterised individuals: the label "Sanguine" described the cynical person; the label "Choleric" described the mystical and/or idealistic person; the term "Phlegmatic" was applied to the skeptic; and "Melancholic" described the pessimist.

The MBTI is based on theory about personality types developed by Swiss psychiatrist Carl Jung. Two Americans, Katherine Cook Briggs and Isabel Briggs Myers, expanded and elaborated on Jung's theory and developed an inventory to help people determine their psychological type. The Myers-Briggs Type Indicator began to be used in 1920 and is today the most widely used psychological inventory in the world.

Psychological type is based on the idea that people have preferences. Our physical preferences include such things as; our preferred hand; our dominant eye; or the foot with which we generally lead.

We have mental or psychological preferences for performing certain tasks. The four basic preferences, or psychological dimensions are:
ENERGISING- How and where you get your attention
ATTENDING - What you pay attention to when you gather information
DECIDING  - What system you use when you decide
LIVING    - What type of life you adopt.

There are two possible choices for each of these four preferences. While we use all eight, we generally favour only one from each of the four basic preferences. The combination of the four preferences results in our psychological type.