According to Wikipedia:

The Myers–Briggs Type Indicator (MBTI) is an introspective self-report questionnaire designed to indicate psychological preferences in how people perceive the world and make decisions.

The MBTI was constructed by Katharine Cook Briggs and her daughter Isabel Briggs Myers. It is based on the typological theory proposed by Carl Jung who had speculated that there are four principal psychological functions by which humans experience the world – sensation, intuition, feeling, and thinking – and that one of these four functions is dominant for a person most of the time. The MBTI was constructed for normal populations and emphasizes the value of naturally occurring differences. "The underlying assumption of the MBTI is that we all have specific preferences in the way we construe our experiences, and these preferences underlie our interests, needs, values, and motivation."