The document discusses Representational State Transfer (REST) and how it relates to HTTP. REST is an architectural style for building distributed systems based on HTTP. It uses HTTP methods like GET, POST, PUT, PATCH and DELETE to operate on resources identified by URIs. Resources can have multiple representations like JSON, XML or HTML. A key constraint of REST is that resources provide hypermedia links to allow state transitions in the application. Following these constraints results in a RESTful design that takes advantage of HTTP as an application protocol.