Party Friends

Jimmy and Lisa always talk about their party friends. I was wondering if these were people who were cool at a party and you became friends with them or if those are the people who always party with you? If it was the former then why wouldn't you call them just friends? If it was the latter then would you hang out with them outside of a party when you aren't hammered or stoned or would that be too awkward. I was just wondering this because the friends I hang out with are also the friends I party with.