REST is acronym for REpresentational State Transfer. It is architectural style for distributed hypermedia systems and was first presented by Roy Fielding in 2000 in his famous dissertation.REST (Representational State Transfer) is an API that defines a set of functions that programmers can use to send requests and receive responses using the HTTP protocol methods such as GET and POST.
Further, resource representations shall be self-descriptive: the client does not need to know if a resource is employee or device. It should act on the basis of media-type associated with the resource. So in practice, you will end up creating lots of custom media-types – normally one media-type associated with one resource.
Guiding Principles of REST
Client–Server
By separating the user interface concerns from the data storage concerns, we improve the portability of the user interface across multiple platforms and improve scalability by simplifying the server components.
Stateless
Each request from client to server must contain all of the information necessary to understand the request, and cannot take advantage of any stored context on the server. Session state is therefore kept entirely on the client.
Cacheable
Cache constraints require that the data within a response to a request be implicitly or explicitly labeled as cacheable or non-cacheable. If a response is cacheable, then a client cache is given the right to reuse that response data for later, equivalent requests.
Uniform interface
By applying the software engineering principle of generality to the component interface, the overall system architecture is simplified and the visibility of interactions is improved. In order to obtain a uniform interface, multiple architectural constraints are needed to guide the behavior of components. REST is defined by four interface constraints: identification of resources; manipulation of resources through representations; self-descriptive messages; and, hypermedia as the engine of application state.
