REST stands for Representational State Transfer. It is a set of design principles for making network communication more scalable and flexible. post 
Roy Fielding analyzed the traits that made the Web more successful than competing Internet protocols. He then envisioned a design framework for making network communication “web-like.”
So REST is a generic set of principles not specific to the Web. It can be applied to other kinds of networks such as embedded systems. REST is also not a protocol since it does not prescribe implementation details.