HyperText Transfer Protocol is the transfer protocol of the World Wide Web, designed to issue requests on URIs and return responses. A HTTP request/response contains a number of metadata (HTTP headers} describing the request/response, and (possibly) a document body (a HTML document, an image, etc).
Part of the HTTP request is the HTTP Method. This tells the server what type of request it is and what action to take. On the Web, the most commonly used methods are the GET, POST and HEAD methods, although the others are defined they are not readily implemented in client or server web software.
Request a resource from a URI. This resource could be a HTML document, an XML document of some grammar, a binary data format, anything. The server finds the document pointed to by the URI and returns it as the body of a HTTP response. GET is synonymous in the database world with a SQL SELECT statement.
The POST method is used to request that the server accept the enclosed entity as a new subordinate of the resource. It should be used for updating a URI, eg. adding information to a messageboard or guestbook, submitting data to server processes, etc. POST is synonymous in the database world with a SQL UPDATE statement.
The PUT method requests that the enclosed entity be stored under the supplied URI. Unlike POST, PUT requests that the entity in the request be the content of the resource at the URI, rather than be data submitted to it. If a URI does not already exist, it is created, if it does exist, the new content is treated as being an update and overwrites the existing document at the URI. PUT is synonymous in the database world with a SQL INSERT statement.
The DELETE method requests to the server that the URI be removed from the network. This could mean to remove the document from the public domain, or to delete it entirely from the server. DELETE is synonymous in the database world with a SQL DELETE statement.
The HEAD method is identical to the GET method, except no content is returned in the response. The metainformation contained in the HTTP headers in response to a HEAD request are identical to the information sent in response to a GET request. The HEAD method is used to check a URI is valid, and/or if it has been updated since it was last requested.
The OPTIONS method request information about the communication options available for that URI.
The TRACE method is used to invoke a loop-back of the request message. TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing or diagnostic information.
The CONNECT method is reserved for use with a proxy that can dynamically switch to being a tunnel.
For more information on the HyperText Transfer Protocol, its syntax and use, see HTTP.
HTTP/1.1 (RFC 2616) - ftp://ftp.isi.edu/in-notes/rfc2616.txt