Back-end services get no glory. Services are stand-alone modules that provide task-oriented processing. As stand-alone modules, they are self-contained, requiring no complicated setup, and no tear-down. Well written services do one thing and do it well. Services can be written by third parties, or by the in-house development team.
Back-end services are callable via HTTP following the specification's standard Request/Response protocol. As such they can easily be called directly using either the GET or POST mechanism, using a browser's URL input, or an HTML <form> tag. With the advent of AJAX—embedded HTTP calls within standard HTML pages—a service becomes the magic back-end that makes all the front-end glitter possible.