Windows 8 (x86 & x64) and Windows Server 2012 support two kinds of applications:
- Windows Store apps (formerly known as Metro) that are written using WinRT APIs and a subset of Win32 APIs, VS 2012 and the Windows 8.0 SDK, and deployed exclusively through the Windows Store. The UI for these apps is very touch-friendly, and
typically makes use of XAML.
- Win32 desktop apps which as always can require a certain minimum OS level so they can be made to run downlevel on Windows 7, Windows Vista, etc. Generally they do not have access to WinRT APIs, only Win32 APIs. Deployment and installation is the same as
it has been for many years.
Windows RT (ARM) supports only Windows Store apps built for the ARM platform.
Windows phone 8 supports a variation of Windows Store apps built for the ARM platform.
You can't write a single EXE that runs as both a Windows Store app and a Win32 desktop app. You can share portions of your codebase between both kinds of EXEs.