The term REST (representational state transfer was first introduced by Roy Fielding, who is one of principal authors of the HTTP 1.0 and 1.1, in his doctoral thesis in 2000.

RESTful API is a simple web service implemented using HTTP and the principles of REST. It focuses on a systems's resources including how resource stats are addressed and transferred over HTTP.

Most RESTful APIs comply 4 main aspects:

• Use HTTP methods (GET, POST, PUT, DELETE) explicitly
• Be stateless
• Expose directory structure-like URIs
• Transfer XML or JSON (JavaScript Object Notation)