Representational state transfer
The core concept of the Web where the base HTTP message is:
- Stateless - any message can be sent to any End Point and must be processed.
- Asynchronous - HTTP was designed to react to user requests as the need is articulated by a user at his own time and place.
Nearly all interactions on the web occur in a burst where users expect that the service end point will remember the last transaction.
Cookies and HTTP headers contain state data to be used from one message to the next.