PostStream is a TStream property that represents the stream containing the data sent in the TIdHTTPRequestInfo as used in the request for the executing HTTP client session. 

PostStream is used in TIdCustomHTTPServer when the client session is executed. PostStream may contain a reference to an existing stream, or may be implicitly created for the executing client session. 

When the request from the client connection has a non-zero ContentLength, PostStream is used to read the indicated number of bytes. Otherwise, all data is read into PostStream until the client connection is closed. 

If the stream is created during execution of the client thread, the contents of PostStream are added to the UnparsedParams property for the client request.

UnparsedParams