The Web is based on a rather simple notion: There are Web servers and there are clients, such as browsers. It’s an asymmetric kind of a connection: Clients connect to servers to request stuff. This breaks when what we need is more interactivity--for example, when our online webmail service notifies us of a new email, an update to a stock tick or news item, or the ring of our virtual phone. To achieve that, we hack our way with things like XHR, SSE and, recently, WebSockets.
While WebRTC is not a mainstream term it is the primary technology contender of the telephony world with more than 2 billion supported browsers. By following a Web model instead of a traditional Telco model. WebRTC eschews a requirement for interoperability in exchange for innovation and choice.