Hyper Text Transfer Protocol (HTTP), the standard protocol for the web. It defines what happens when a client (web browser) connects to a server (web server). It breaks down to four steps...

• Client establishes a connection to a port on a server (port 80 if no port is specified)
• Client Makes a request - GET/HEAD/POST/PUT/DELETE/TRACE/CONNECT
• Server makes a response - indicating what happened.
• Connection is closed