Windows 8 and Windows 8 Pro will work on x 86 PCs and tablets (both 32 and 64 bit). In addition to core features like touch screen support, they’ll include an updated Windows Explorer, Task Manager, better multi-monitor support and the ability to switch languages on the fly. Windows 8 is really for consumer use; Windows 8 Pro is more for tech enthusiasts and professionals who want things like encryption, virtualization and PC management.
Windows RT will only be available pre-installed on ARM-powered PCs and tablets. It will offer touch-optimized desktop versions of Word, Excel, PowerPoint, and OneNote, and allow for app development on the new Windows runtime.