HTTP (Hypertext Transfer Protocol) is a data transfer protocol. Originally it was meant to transfer hypertext documents in HTML format. Nowadays it is widely used to receive information from web sites. HTTP is also used as a transport for others application level protocols such as SOAP, XML-RPC, WebDAV.
The main manipulation object in HTTP is the resource indicated by the URI (Uniform Resource Identifier) in the HTTP client inquiry to HTTP server. Usually these sources are the files stored on the server, but it can also be logic objects or something abstract. The particularity of HTTP protocol is the possibility to indicate the mechanism of representation of the same resource with different parameters (format, code, language, etc.) in the inquiry and in the response. Precisely because of the possibility to indicate the mechanism of message coding, the client and the server can exchange binary data, even though this protocol uses text.