Introversion and extroversion are not about whether we’re shy or outgoing. They’re about our sensitivity to stimulation and how our energy levels are affected by social interaction. Susan Cain offers a beautiful way of thinking about this (as relayed by Simon Sinek).

Introverts wake up in the morning with five coins. With every social interaction they spend a coin. At the end of the day, they feel depleted.

Extroverts wake up in the morning with no coins. With every social interaction they gain a coin. At the end of the day, they feel rich.

Not only is this a useful framework for understanding our own introversion or extroversion, it’s useful in better understanding our friends, family members, and colleagues.