As you learned in Chapter 1, a Silverlight application is actually a package of files that's archived using ZIP compression and stored as a single file, with the extension .xap. In a simple application, the XAP file has little more than a manifest (which list the files your project uses) and your application assembly. But you can place something else in the XAP file: resources.
A XAP resource is a distinct file that you want to make available to your compiled application. Common examples include graphical assets—images, sounds, and video files that you want to display in your user interface.
Using resources can be unnecessarily complicated because of the wealth of different options Silverlight provides for storing them. Here's ...