Windows 8 (for x86, Intel/AMD)
Windows 8 Pro (for x86, Intel/AMD)
Windows RT (for ARM)
Windows 8 (yes, just Windows 8) is the home version for x86 Intel and AMD PCs. The features you do and don’t get mostly make sense; joining a domain, encrypting your disk with BitLocker and being able to log into your PC remotely are business features.
You can connect to a PC at work from a Windows 8 system, with Remote Desktop or a VPN, you can combine multiple hard drives into one storage ‘pool’ that has multiple copies of your files and you can mount VHD and ISO images as if they were hard drives – but you can’t boot from a VHD file.
And anyone who speaks more than one language or travels between countries will be delighted that you can switch not just the keyboard but the Windows interface from one language to another without paying extra.
Windows 8 Pro
What doesn’t immediately make as much sense is that Media Center not included with Windows 8; it’s “an economical media pack add-on” that’s only available for Windows 8 Pro, which is otherwise for business users (or enthusiast users). Again, Windows 8 Pro is for for x86 Intel and AMD PCs.
Although Media Center has dedicated fans, only 6% of Windows 7 users ever launch it and only 25% of those use it for more than ten minutes at a time.
Microsoft has to pay licences for the codecs used in Media Centre, including Dolby technology. So it looks like Microsoft made it a paid add-on.
All three versions of Windows 8 run Metro-style (also now known as Microsoft design style) applications written in WinRT, the new Windows RunTime programming framework, which is also what Windows RT is named for. Windows RT will come pre-installed on ARM devices like Microsoft Surface, you won’t be able to install it yourself.
This is what was previously called Windows on ARM. It has both the Microsoft design style Start screen and the Windows desktop, with Task Manager and Explorer and support for multiple monitors (remember Windows RT devices won’t be just tablets and they’ll have connectors like HDMI).