Command is a read-only String property that represents the HTTP command received in the HTTP request, like "GET", "POST", or "HEAD". 

Use RawHHTTPCommand to access the entire HTTP command in it's original form. 

Command is updated when TIdCustomHTTPServer reads the HTTP request from an executing HTTP client session. Command can be used in TIdCustomHTTPServer event handlers, like OnCommandGet and OnCommandOther, to determine the HTTP command that originated the request.

TIdCustomHTTPServer 

TIdHTTPServer 

RawHTTPCommand