From the HTTPD specs at
The request has succeeded. The information returned with the response is dependent on the method used in the request, for example:
- GET an entity corresponding to the requested resource is sent in the response;
- HEAD the entity-header fields corresponding to the requested resource are sent in the response without any message body;
- POST an entity describing or containing the result of the action;
- TRACE an entity containing the request message as received by the end server.