Hypertext Transfer Protocol.
The Hypertext Transfer Protocol (HTTP) is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. (Source: Wikipedia)
HTTP is a formal method that computers use to talk to each other on networks, such as the Internet. In the OSI Layered Model it is part of the application layer, which means that it is at the most abstract level of communication in a network. It is at the core of the Internet. You may notice that most URLs begin with the text
Well, that is the protocol header for a URL, and it says “Use HTTP.” Pretty much every webpage starts with this, which proves that HTTP is at the core of the Internet!
HTTP is a protocol that, as its name implies, transfers hypertext (such as HTML pages).
HTTP is carried out in sessions between a client (your computer) and a host/server (a website). The client contacts the host and issues a request. The host returns with a response. Repeat.
Wikipedia has an example session here.
The client has nine options for requests it can make. The most common ones are GET and HEAD. GET asks the server for something. “Hey server, can I have http://google.com/?” The server then replies. HEAD is similar, but it just asks for the “top” of the page. The “header” data, so to speak.
The server then responds with a status code, followed by a bunch of data. Ever seen “ERROR 404: PAGE NOT FOUND?” 404 is a status code! It means… page not found. Who would have guessed? Other error codes include 403: Forbidden, 200: OK, 301: Moved Permanently, and 413: Requested Entity Too Large (for when you send the request “GET Your%20Mother http/1.1”).