Answer - A .xap file is a Silverlight-based application package (.xap) that is generated when the Silverlight project is built. A .xap file is the compressed output file for a Silverlight application. The .xap file includes AppManifest.xaml, the compiled output assembly of the Silverlight project (.dll), and the resource files referred to by the Silverlight application: • Web pages like .aspx files and .html files use Silverlight components by loading .xap files using the tag in HTML or by using the tag in ASP.NET pages. • ".xap" files (pronounced "zap") use the standard Zip compression algorithm to minimize client download size. Rename this file to SilverlightTest.zip and open it using any decompression tool. You can see that this is just like any other zip file, and it includes the project's output DLL and another file called "AppManifest.xaml".