In windows 8.1 start screen, if I go to the all apps view & sort by category, the first category is 'desktop'. What determines which apps are listed here? Only some of my desktop apps are listed. Can I edit the list? Likewise, if I sort by name, the first group of apps includes only a subset of all my apps - can I edit that list?
Every WindowsRT-App ( = Metro/ModernUI) has to provide StartTiles in at least two sizes (I think). So there you have your distinction betwenn "normal" desktop-applications which are shown in the desktop-category and ModernUI-Apps.
The desktop category shows desktop apps that aren't in their own folder inside the Start menu folder. So Word 2013 shows in the Office 2013 folder, but Adobe Reader is in the desktop one.