People can be what you might call introverts with a capital I (aka "very introverted") or they might be outgoing in some situations with some introverted tendencies. Introversion exists on a continuum with extroversion, and most people tend to lie somewhere between the two.

Is Introversion and extraversion a real thing?

Most simply, Jung conceived of introverts as drawing energy from being alone, whereas extraverts draw it from their surroundings and relationships. ... To be sure, diehard introverts and extraverts do exist, but they're exceptions, and they may be worse for it.

Do extroverts even exist?

To be sure, diehard introverts and extroverts do exist, but they're exceptions, and they may be worse for it. In fact, such extreme leanings could be the result of what psychologist Carol Dweck calls a "fixed mindset."