HTTP – Hypertext Transfer Protocol

An application-level protocol for distributed, collaborative, hypermedia information systems (text, graphic images, sound, video, and other multimedia files) on the World Wide Web.

It’s fundamentally used by two actors:

Client
A program that establishes connections for the purpose of sending requests

Server
An application program that accepts connections in order to service requests by sending back responses

Overall Operation

The HTTP protocol is a request/response protocol.

  1. A client sends a request to the server in the form of a request method, URI, and protocol version, followed by a MIME-like message containing request modifiers, client information, and possible body content over a connection with a server.
  2. The server responds with a status line, including the message’s protocol version and a success or error code, followed by a MIME-like message containing server information, entity metainformation, and possible entity-body content

Source: https://tools.ietf.org/html/rfc2616#section-1.3