WebRTC is the latest in peer to peer communications via the browser. We are talking about Chat, Video and Audio completed transmitted via the browser, signaled and connected using servers still on the back-end.
Even though a great new piece of ingenuity it still requires a server or a service paid to commercial servers in order to run effectively. This exchange is called Signaling.
Which is basically is a series of processes allowing each peer browser to Call and Respond to each others, even though passing very little data between in order to work.