a party or a gathering of any people for reasons that are usually happy where the poeple interact and generally have a good time. a celebration can be for a birthday, holiday, promotion. celebrations can also be for no reason other then to see friends.
Person one: hey i am haveing a pool party wanna come?
person two: whats it for?
person one: no reason, i used wanted to have a summer celebration with my friends!
person two: awesome be there!