HTTP is the protocol that allows for sending documents back and forth on the web. A protocol is a set of rules that determines which messages can be exchanged, and which messages are appropriate replies to others.
An HTTP proxy is a program that acts as an intermediary between a client and a server. It receives requests from clients, and forwards those requests to the intended servers. When a client uses a proxy, it typically sends all requests to that proxy, instead of to the servers in the URLs. Requests to a proxy differ from normal requests in one way: in the first line, they use the complete URL of the resource being requested, instead of just the path. For example,
GET http://www.somehost.com/path/file.html HTTP/1.0
That way, the proxy knows which server to forward the request to.
HTTP verbs tell the server what to do with the data identified by the URL. The request can optionally contain additional information in its body, which might be required to perform the operation for instance, data you want to store with the resource.
GET / HTTP/1.1
means the GET method is being used, while
DELETE /clients/anne HTTP/1.1
DELETEmethod is being used.
Other HTTP verbs are PUT,DELETE,OPTIONS,HEAD.
HTTP Status codes
The status code is a three-digit integer, and the first
digit identifies the general category of response:
1xx indicates an informational message only
2xx indicates success of some kind
3xx redirects the client to another URL
4xx indicates an error on the client's part
5xx indicates an error on the server's part