Introversion/extroversion is probably the most robust aspect of personality--virtually every personality spectrum includes an introversion/extroversion dimension. However, a lot of people probably misinterpret what it actually means. The best explanation I've heard is that it's essentially about how you "recharge": introverts recharge by being alone, and being in a large social function is draining; extroverts recharge by being in large social functions, and are drained by being alone.
Of course, the annoying thing about US culture in particular is that introversion is often seen as something undesirable--witness all the articles about how introverts should learn to be extroverts, where you don't really see the inverse about how extroverts should learn to be introverts.
Of course, the annoying thing about US culture in particular is that introversion is often seen as something undesirable--witness all the articles about how introverts should learn to be extroverts, where you don't really see the inverse about how extroverts should learn to be introverts.