As title, could you tell me why HttpRequest structure parameter filename?
The code example:

 HttpRequest request=new HttpRequest (" default. Aspx ", "http://localhost/0512/3", null); 

I'm a little don't understand is, usually we request a page url, then various analytical open aspx page
But the code above the first parameter corresponds to a file,
Excuse me, this is why the HttpRequest and we understand what is the difference between request?