This article deals with the psychological term Introversion. If you are looking for the games developer, see Introversion Software
The terms Introvert and Extrovert (originally spelled Extravert by Carl Jung, who invented the terms) are referred to as "attitudes" and show how a person orients and receives their energy. In the Extraverted attitude the energy flow is outward, and the preferred focus is on people and things, whereas in the Introverted attitude the energy flow is inward, and the preferred focus is on thoughts and ideas.
See also: Myers-Briggs Type Indicator