IMVU is an online social entertainment destination where members use 3D avatars to meet new people, chat, create and play games. This is not a fully realised 3D world like Second Life or even Onverse - rather it's a platform for the user access chat rooms via their avatar. Rooms and avatars can be decorated as you like, but avatars can only be customised so far. Decoration by way of clothes, pets, rooms, poses and accessories is preferred, both of which you need to buy by using Credits (which are bought with real money), or create (and/or later sell).
This is a world entirely of "3D Rooms" and little else. Your room is actually described as a "scene" and you can have your avatar in more than one chat-room simultaneously (have fun keeping track of the conversations) and even be dressing up or shopping as well. Movement is by selecting predesignated points in a room, like spots on the floor or furniture. Chatting is by text in speech balloons.
A fairly straightforward chatting host, where dancing, shopping, flirting and other social activities (enabled no doubt by custom poses) are pretty much all you can do.