In other words, REST is a set of architectural principles for serving resources, usually over HTTP. It is so ingrained in web development, and so standardized, that it feels strange when we do not see it.
What it means for an API to be RESTful | Andros Fenollosa
I’ve been pretty interested in this as a stand-in for single sign on when no personal or secure information needs to be transmitted. It can be used to stitch together web pages that are doing something for someone using a browser.