The document discusses Representational State Transfer (REST) as an architectural style for building distributed hypermedia systems. It describes key REST principles such as giving every resource an identifier, linking resources together through hyperlinks, using standard HTTP methods like GET, PUT, POST and DELETE, and communicating statelessly. The document also compares REST to other styles like WS-* and contrasts how REST uses URIs and HTTP while WS-* uses SOAP. It provides examples of companies and projects using REST.