Is There a Difference Between Group Chats and Private Chats?

Group chats have become a pretty major, what do you call it, persistent, but ad hoc. One is the ad hoc work group thing that feels a little bit wrong. Another one I think of that goes a very literal approach with trying to create a more virtual online meeting place is Gather Town. Those are two maybe interesting examples of ways that some of these call them like real world ways of communicating and working as we might do in a physical office.