I just want to point out that introvert is not the same as shy. This is a very common misconception. An introvert doesn't have to be a shy person at all. A shy person will be uncomfortable in many (or even most) social settings. An introvert can enjoy being surrounded by people in social settings, but may feel exhausted afterward. An extrovert will feel energized by this. Introverts generally need more "me time" to avoid emotional exhaustion.
Introvert/extrovert isn't about being shy/outgoing but whether you feel drained or energized after social settings with lots of people. This could even be after normal day at work.
Shy/outgoing and introvert/extrovert are two completely different things.
A person can be:
-A shy introvert.
-An outgoing introvert.
-A shy extrovert.
-An outgoing extrovert.
A shy person would have difficulties with performing on a stage. An outgoing introvert would not have a problem with this at all, but may feel more drained afterwards than an extrovert.
Introverts do tend to spend more time alone, or prefer the company of smaller groups of people. Not because they're shy, but because larger groups of people can make them feel exhausted.