static files like html files or images the web server simply reads the file from its local hard drive and sends it to the browser. however for dynamic files such as aspx pages this is obviously not good enough. if the web server were to send the aspx file directly to the browser as a text file you wouldn't have seen the current date and time in the browser but instead you would haveseen the actual code (<%:DateTime.Now.ToString() %>). So, instead of sending the file directly the web server hands over the request to another piece of software that is able to process the page. this is done with a concept called application mapping or handler mapping where an extension of a file (.aspx in this example) is mapped to an application that is capable of handling it. In the case of an .aspx page the request is eventually handled and processed by the asp.net run time, part of the Microsoft .net framework designed specifically to handle web requests
