Could be as trivial as a type of food, a TV show, or something more serious.
The key difference between introverts and extroverts is that for introverts social interactions drain our mental energy while extroverts are energized by interactions.
One key thing to remember here is introvert/extrovert isn’t about the level of shyness or anxiety though. You could be an extremely outgoing introvert or a shy extrovert. It truly is only about the relationship between your mental energy and social interaction. The comment above sounds more like social anxiety than introversion, though could be both.