One thing I learned from reading Jung and not just the MBTI stuff based on his work is his core distinction between introversion and extroversion:

Introverts have an inner model of the world. Extroverts rely directly on the world.

It doesn’t mean that extroverts like people more or that introverts necessarily prefer being alone. It’s just that for extroverts, when nothing external is happening it’s like a little death. And for introverts, we need down time to reconcile our inner model with all of the day’s external stimulation.