REST enables any interface between systems using HTTP to obtain data and generate operations on those data in all possible formats, such as XML and JSON.
REST is a stateless client/server protocol. That means any HTTP request contains all the necessary information to execute, which and neither the client nor the server needs to remember any previous state to satisfy it.
REST has become a software development standard. Pretty much everyone out there – including Facebook, Google, Twitter – has begun using REST and as a result, there is a vast knowledge and experience base out there among software developers.