Getting up in front of a crowded room and giving a presentation, embarrassing yourself (for fun or not) in public, or going on a first date with someone new can have the potential to make just about anyone a little bit nervous, but for some people who struggle with high-functioning social anxiety, even seemingly lower-stakes social situations or interactions can cause some concern. For those who are high-functioning, this doesn't necessarily mean that they'd skip out on social events entirely, which is partially why it can be hard to suss out. The signs you have high-functioning social anxiety aren't as obvious or extreme as those that go along with a straightforward diagnosis, but can difficult for people to handle all the same.
For people with high-functioning anxiety disorders, explaining what they're dealing with to those who don't understand that same experience can be hard. They don't have a diagnosed anxiety disorder, necessarily, and typically appear unaffected by anxiety to outside observers. Basically, people don't suspect that they're dealing with social anxiety, even though they are. Knowing that what you're dealing with is something more than what others might be, however, can give you a bit of peace of mind. It doesn't make the symptoms easier, but gives you a sort of explanation for why things are the way that they are, and maybe spurs you talk to someone about how to handle it.