A processor put forth by Intel in the 1982 and first used in the IBM PC/AT in 1983. It was an improvement over the earlier 8086 and 8088 in that it was 16 bits internally and externally as opposed to the 8086 which was 8 bits externally and the 8088 which was 8 bits all around.
It was available in 8, 10, 12, and 16 mHz models, with compatible version of it produced by AMD and NEC that eventually went has high as 24 mHz. It usually shipped in either a Quad Flat Package design from Intel and AMD or a DIPP from NEC.
With 16 bit addressing also came a 16 megabyte memory ceiling (versus 1 MB for the 8088), 16 bit ISA expansion slots and even primitive versions of protected mode, but it was difficult to work with and was never fully exploited.
Mostly the 286 was used just as a faster 8086, especially since its design could accept and 8087 FPU.