What is the difference between Windows 8 and Windows RT?
Solution 1:
From the Windows Blog post "Announcing Windows 8 Editions":
For PCs and tablets powered by x86 processors (both 32 and 64 bit), we will have two editions: Windows 8 and Windows 8 Pro.
Windows RT is the newest member of the Windows family – also known as Windows on ARM or WOA, as we’ve referred to it previously. This single edition will only be available pre-installed on PCs and tablets powered by ARM processors.
Wikipedia also has nice pretty tables with more details on the available features.
Full list of features in each version from the Microsoft blog post:
╔════════════════════════════════════════════════╦═══════╦═════╦═════╗
║ Feature Name ║ Win 8 ║ Pro ║ RT ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Upgrades from Windows 7 Starter, ║ x ║ x ║ ║
║ Home Basic, Home Premium ║ ║ ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Upgrades from Windows 7 Professional, Ultimate ║ ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Start screen, Semantic Zoom, Live Tiles ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Windows Store ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Bundled Modern UI/Metro Apps (Mail, Calendar, ║ ║ ║ ║
║ People, Messaging, Photos, SkyDrive, Reader, ║ x ║ x ║ x ║
║ Music, Video) and support for other Store Apps ║ ║ ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Microsoft Office Home & Student RT included ║ ║ ║ x ║
║ with OS (Word, Excel, PowerPoint, OneNote) ║ ║ ║ * ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Internet Explorer 10 ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Device encryption ║ ║ ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Connected standby ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Microsoft account ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Desktop and support for Desktop apps ║ x ║ x ║ † ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ SmartScreen ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Windows Update ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Enhanced task manager ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Switch languages on the fly w/ language packs ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Better multiple monitor support ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Storage spaces ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Windows Media Player ║ x ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Windows Media Center (separate download) ║ x ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Exchange ActiveSync ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ File history ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ ISO / VHD mount ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ VHD booting ║ x ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Mobile broadband features ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Picture password ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Play To device ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Remote Desktop client ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Remote Desktop host ║ ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Refresh and reset your PC ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Snap ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Touch and Thumb keyboard ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Trusted boot ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ VPN Client ║ x ║ x ║ x ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ BitLocker and BitLocker To Go ║ ║ x ║ ‡ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Client Hyper-V ║ ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Domain join ║ ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Encrypting File System ║ ║ x ║ ║
╠════════════════════════════════════════════════╬═══════╬═════╬═════╣
║ Group Policy ║ ║ x ║ ║
╚════════════════════════════════════════════════╩═══════╩═════╩═════╝
* Office Home & Student RT does not include support for Macros, Add-Ins, Forms and other features as listed in the FAQ.
† Only bundled Microsoft applications such as Notepad, Paint etc. can be executed in Desktop mode on Windows RT.
‡ Windows RT has no UI and very limited support for managing Bitlocker To Go drives (cut down version of manage-bde command is available).
If you're not sure whether a given program will work on your version of Windows, you can find more information in How can I tell which versions of Windows 8 a program will work on?
Solution 2:
Windows RT is compiled to use an ARM CPU and only runs Metro apps. Windows 8 Pro is the standard Windows OS that runs on x86 processors (Intel, AMD, etc). It runs Metro apps as well as existing Windows applications.
Solution 3:
Windows RT is a version designed for ARM Processors, machines like tablets. Windows 8 will be the normal x86-x64 type.