For example, a request for
http://server/application/Products.aspx?id=4 maps to a file that is named Products.aspx that contains code and markup for rendering a response to the browser. The Web page uses the query string value of id=4 to determine what type of content to display, but the value is likely to have little meaning to the user.
In ASP.NET routing, you define URL patterns that contain placeholders for values that are used when you handle URL requests. At run time, the pieces of the URL that follow the application name are parsed into discrete values, based on a URL pattern that you have defined. For example, in the request for
http://server/application/Products/show/beverages, the routing parser can pass the values Products, show, and beverages to a handler for the request. In contrast, in a request that is not managed by URL routing, the /Products/show/beverages fragment would be interpreted as the path of a file in the application.