x86 denotes a family of instruction set architectures based on the Intel 8086 CPU. The 8086 was introduced in 1978 as a fully 16-bit extension of Intel's 8-bit based 8080 microprocessor and also introduced memory segmentation to overcome the 16-bit addressing barrier of such designs. The term x86 derived from the fact that early successors to the 8086 also had names ending with "86". Many additions and extensions have been added to the x86 instruction set over the years, almost consistently with full backward compatibility. The architecture has been implemented in processors from Intel, Cyrix, Advanced Micro Devices, VIA and many other companies.
The term is not synonymous with IBM PC compatibility as this implies a multitude of other computer hardware; embedded systems as well as general-purpose computers used x86 chips before the PC-compatible market started, some of them before the IBM PC itself.