This documentation is for Live Forms 7.3 Not for you? Earlier documentation is available too.
Integrating with HTTP Servers
 can POST form or workflow data to your web server for processing. There are two options available Form Action Post and Doc Action Post. The difference between the two is that the Form Action POST displays the response from the web server to the user whereas the Doc Action POST does not.
Processing form data POSTed to your web server is described in the  Submissions Stored Outside of Live Forms.