SPA stands for Single Page Application.
In the web, when people press a link on a page, they usually get redirected to another page. In recent years, a trend has grown where such links update only small parts of the screen instead of loading a full page. This adds more interactivity to the web and enables to easily wrap web services as mobile applications.
WebRTC lends itself to this technique of development since leaving a page tears down an existing call.
