I think this is a thoughtful definition:
Extraversion is "the act, state, or habit of being predominantly concerned with and obtaining gratification from what is outside the self". Extraverts tend to enjoy human interactions and to be enthusiastic, talkative, assertive, and gregarious. They take pleasure in activities that involve large social gatherings, such as parties, community activities, public demonstrations, and business or political groups. Politics, teaching, sales, managing and brokering are fields that favor extraversion. An extroverted person is likely to enjoy time spent with people and find less reward in time spent alone. They tend to be
energized when around other people, and they are more prone to boredom when they are by themselves.
Introversion is "the state of or tendency toward being wholly or predominantly concerned with and interested in one's own mental life". Some popular writers have characterized introverts as people whose
energy tends to expand through reflection and dwindle during interaction. This is similar to Jung's view, although he focused on psychic energy rather than physical energy. Few modern conceptions make this distinction.
The common modern perception is that introverts tend to be more reserved and less outspoken in groups. They often take pleasure in solitary activities such as reading, writing, using computers, hiking and fishing. The archetypal artist, writer, sculptor, engineer, composer and inventor are all highly introverted. An introvert is likely to enjoy time spent alone and find less reward in time spent with large groups of people, though he or she may enjoy interactions with close friends. Trust is usually an issue of significance: a virtue of utmost importance to an introvert choosing a worthy companion. They prefer to concentrate on a single activity at a time and like to observe situations before they participate, especially observed in developing children and adolescents. They are more analytical before speaking. Introverts are easily overwhelmed by too much stimulation from social gatherings and engagement, introversion having even been defined by some in terms of a preference for a quiet, more minimally stimulating environment.
Introversion is not seen as being identical to shy or to being a social outcast. Introverts prefer solitary activities over social ones, whereas shy people (who may be extroverts at heart) avoid social encounters out of fear, and the social outcast has little choice in the matter of his or her solitude.
Ambiversion Although many people view being introverted or extroverted as a question with only two possible answers, most contemporary trait theories measure levels of extraversion-introversion as part of a single, continuous dimension of personality, with some scores near one end, and others near the half-way mark. Ambiversion is a term used to describe people who fall more or less directly in the middle and exhibit tendencies of both groups. An ambivert is normally comfortable with groups and enjoys social interaction, but also relishes time alone and away from the crowd.
Extraversion and introversion - Wikipedia, the free encyclopedia