strophe.jinglejs is a webrtc connection plugin for strophe.js that uses jingle.js. Strophe is a popular library for writing XMPP client applications that run on any of the current popular browsers. Instead of the native TCP binding, strophe.js uses BOSH (Bidirectional-streams Over Synchronous HTTP, a variant of long polling) to connect to an XMPP server. Besides enabling anyone to build (federated) IM applications, this opens up the browser as an addressable endpoint for two-way exchange of structured messages, including presence and publish-subscribe applications.
This plugin makes it possible to negotiate audio/video streams via XMPP and then relinquish control to the WebRTC support of browsers like Firefox and Chrome for the actual out-of-band media streams. XMPP/Jingle you get the authenticated, secured and federated media signaling, whereas WebRTC gives you an API to set up the media streams using RTP/ICE/STUN and provide access to cameras and microphones.
The "Silo-Free WebRTC" talk from the 2013 Realtime Conference explains this very well. The XMPP specific part starts around 17:00.
Strophe.jinglejs in the wild: