Read original post by Tony Champion at .NET Rocker
If you have spent any time at all working on Windows Store apps, then you have become familiar with the package.appxmanifest file. This is a very important part of your application and helps define how your application will run within Windows 8. At a very basic level, this is where you set things like the name, description, and the default logos for your application. However, the meat of the AppxManifest is the capabilities and declarations sections. These sections are where you inform Windows 8 what level of access your application requires to run on a user’s machine. This provides security and transparency to the user. For instance, the user might want to know what a weather application needs access to the computer’s webcam.