As a kind of reaction to Google+, Facebook just rolled out two features today: group text chat and integrated video chat courtesy of Skype.
The video chat is interesting, because you don't need to download a Skype client - all you do is log in to your Facebook account and start a video chat with anyone on your friends list. It's unclear whether or not you can call an actual Skype user, even though the underlying technology is Skype.
Although they say that there's no client you have to install, like Skype, there actually is a plugin setup process that's, well, essentially like downloading and installing a client, albeit a browser plugin client. The videos pop up in a separate window you can move around your desktop, and you can select the active microphone in the video window without having to restart the call.
Group chat is basically just how group chats work on any other platform. You start a chat, then start adding additional people to the chat. It takes place in the same Facebook IM window that you've been using for a while.