As written on REST API Tutorial:
REST is acronym for REpresentational State Transfer. It is architectural style for distributed hypermedia systems ans was first presented by Roy Fielding in 2000 in his famous dissertation.
All APIs use JSON format for requests and responses.
We have 2 kind of APIs.
Resource CRUD (see Using HTTP Methods for RESTful Services for more details)
All connections are done through HTTPS (by default TLS 1.2 and could be negotiated to TLS 1.1 only).