What is HTTP (HyperText Transfer Protocol)?
HTTP is the protocol of the Web, by which Servers and Clients (typically browsers) communicate. An HTTP transaction comprises a Request sent by the Client to the Server, and a Response returned from the Server to the Client. Every HTTP request and response includes a message header, describing the message. These are processed by the HTTPD, and may often be mostly ignored by CGI applications (but see below). A message body may also be included: 1) A HEAD or GET request sends only a header. Any form data is encoded in an HTTP_QUERY_STRING header field, which is available to the CGI program as an environment variable QUERY_STRING. 2) A POST request sends both header and body. The body typically comprises data entered by a user in a form. 3) A HEAD request does not expect a body in the response. 4) A GET or POST request will accept a response with or without a body, according to the header. The body of a response is typically an HTML document.
