REST is an acronym for REpresentational State Transfer and an architectural style for distributed hypermedia systems. Like other architectural styles, REST has its guiding principles and constraints. These principles must be satisfied if a service interface needs to be referred to as RESTful. A Web API (or Web Service) conforming to the REST architectural style is a REST API.
REpresentational State Transfer – is an architectural style that makes use of existing and widely adopted technologies, specifically HTTP, and does not create any new standards. REST can structure data into XML, YAML, or any other machine-readable format, but usually, JSON is preferred.