By "party", I mean a physical social gathering of people for the purposes of having fun. It may be used in a sentence as "I am throwing a party!" or "Let's party!".
Basically what I am trying to say is the default "party".
I've never been to any, and I have no idea how people spend their time on parties, so I am curious how you did.
If you've ever been to a festival or fair, think of it as a miniature version of that. It's mostly just a hangout for people to do fun things they wouldn't do everyday, since they feel the day is exceptional.