Windows 8 comes in four different editions that support both x86 and ARM-specific platform, there are two platforms that Windows 8 is supported, the ARM processor platform and the x86 platform.
The ARM processor platform - Windows 8 RT, is the first Windows client operating system designed to support ARM processor architecture such as tablets and phones. This version is available only as pre-installed operating on ARM processors devices which usually touch-enabled devices or platform.
The x86 platform - Windows 8 comes in there editions that support x86 platform, Windows 8, Windows 8 Pro and Windows 8 Enterprise. Each edition Windows 8 is available in both 32-bit and 64-bit versions with 64-bit version having several advantages as compared to 32-bit, such as performance improvement, efficient memory utilization, support of new Windows 8 features. The features comparison of both Windows 8, Windows 8 Pro & Windows 8 RT is available on Announcing the Windows 8 Editions.