HTTP is an application layer network protocol built on top of TCP. HTTP clients (such as Web browsers) and servers communicate via HTTP request and response messages. The three main HTTP message types are GET, POST, and HEAD.
HTTP utilizes TCP port 80 by default, though other ports such as 8080 can alternatively be used.
The current version of HTTP in widespread use - HTTP version 1.1 - was developed to address some of the performance limitations of the original version - HTTP 1.0. HTTP 1.1 is documented in RFC 2068.