Microsoft has announced that there will be three flavors of Windows 8 for consumers: Windows 8, Windows 8 Pro, and Windows RT.
The default version — 32- and 64-bit Windows 8 for x86 PCs and tablets — replaces Windows 7 Home Basic and Home Premium. Windows 8 Pro, with features like BitLocker and Remote Desktop, replaces Windows 7 Professional and Ultimate . There will also be an Enterprise edition of Windows 8, for enterprise customers.
Windows RT has a feature set similar to normal Windows 8, but it lacks Storage Spaces, Windows Media Player, and it can’t install x86/64 software (obviously). Windows RT comes with a free copy of Microsoft Word, Excel, PowerPoint, and OneNote, while Windows 8 and Pro do not.
Windows RT will only be available as a pre-installed OS.