The generic term x86 refers to the most commercially successful instruction set architecture in the history of personal computing. It derived from the model numbers, ending in "86", of the first few processor generations backward compatible with the original Intel 8086. Since then, many additions and extensions have been added to the x86 instruction set, almost consistently with full backwards compatibility. The architecture has been implemented in processors from Intel, Cyrix, AMD, VIA, and many others.
As the x86 term became common after the introduction of the 80386, it usually implies a binary compatibility with the 32-bit instruction set of the 80386. This may sometimes be emphasized as x86-32 to distinguish it either from the original 16-bit x86-16 or from the newer 64-bit x86-64 (also called x64). Although most x86 processors used in new personal computers and servers have 64-bit capabilities, to avoid compatibility problems with older computers or systems, the term x86-64 is often used to denote 64-bit software, with the term x86 implying only 32-bit.
Today, the x86 architecture is ubiquitous among desktop and notebook computers, as well as a growing majority among servers and workstations. A large amount of software supports the platform, including OSs such as MS-DOS, Windows, Linux, BSD, Solaris, and Mac OS X. The architecture is relatively uncommon in embedded systems and low-cost niches such as appliances and toys lack any significant x86 presence. Simpler 16-bit x86 chips are more common here, but AMD's Geode and the new Intel Atom are examples of 32-bit designs used in this segment.
Contrary to some popular belief, x86 is not synonymous with IBM PC compatibility as this also implies a multitude of other hardware, albeit with some of it standardized. For instance, the original Xbox was designed around an x86 processor but security restrictions led to software requirements making it incapable of simply running standard code designed for other IBM PC compatible systems. Also, the GRID Compass laptop (one of the first on the market), and many others, used x86 chips before the IBM PC compatible market even started.