I am reading a book about introversion and here's some of what I've taken away from it so far:

-Introversion vs. extroversion is, for the most part, genetic or innate rather than being learned. Temperament tends to stay relatively constant throughout a person’s life.
-Introversion and extroversion may be the result of different levels of sensitivity to stimuli, i.e. introverts are more sensitive and thus get overwhelmed more easily and need more downtime, while extroverts are less sensitive and so feel bored when they’re not taking in high levels of stimuli. This theory is backed up by research into the actual brain structure of introverts and extroverts.
-Extroversion may also be caused by a sensitivity to rewards. Extroverts experience higher levels of joy and excitement when something good happens or is about to happen to them, causing them to seek out potentially rewarding experiences less discriminately and more confidently than introverts.
-Introverts and extroverts have different leadership styles and different strengths. One’s not better than the other; the ideal environment has an equal number of introverted and extroverted leaders or members.