Windows 8 has some good news for you. To eliminate confusion over multiple versions of Windows OS (like what we saw in Windows 7), Microsoft has said that it's latest avatar of flagship Windows avatar, Windows 8 will have only four versions. The versions will be targed to different user segments..
- For home use called Windows 8
- For business use called Windows 8 Pro
- For big enterprises Windows 8 Enterprise
- For ARM Chips called Windows RT
More on 4 versions of Windows 8: - http://en.wikipedia.org/wiki/Windows_8_editions
For most people buying an OS for a traditional desktop or laptop, the choice will be between just two versions. The version called simply "Windows 8" is designed for home users. "Windows 8 Pro" is for business users and includes features for encrypting a file system, virtualization, and domain management.
"Windows RT" is the new name for what had been called Windows on ARM. You won't be able to purchase it on its own; It'll come preinstalled on PCs and tablets that run ARM processors. Windows RT will be incompatible with traditional X86/64 desktop software. Instead, it'll run touch-oriented apps based on Windows Runtime (or WinRT), Microsoft's programming model for mobile apps. Apps for the touch-oriented Metro interface are built using Windows Runtime.
Windows RT will come with special touch-oriented versions of Microsoft Word, Excel, PowerPoint, and OneNote.
The final version of Windows 8 won't be available for most consumers.