This refers to Windows 8 and Windows 8.1 apps only. Use [Windows-10-Universal] for Windows apps that target Windows 10. Use [winrt-xaml] for Windows XAML-related questions.
Windows Store apps (formerly Metro-style applications) are built on the Windows Runtime (WinRT) and are available on the Windows Store. They target Windows 8 and Windows RT using .NET for Windows Store Apps or html/css and are immersive full-screen applications.
- Stackoverflow.com Wiki