Microsoft Silverlight runs client-side, meaning, it does not run on the web server it runs in a user's web browser. You have to have a method to communicate between the web server that launches the Silverlight application, and the Silverlight application running in the user's web browser. This communication is usually performed using web services.
When you create Silverlight applications, you may discover that you need security, membership management, email, and logging. Implementing these supporting elements can require more time than creating the Silverlight application itself.
SilverlightDesktop provides a framework that allows you to create modules that contain only the custom functionality you need. SilverlightDesktop.net handles the security, membership and role management, as well as providing email and logging support.