RESET is generally a pin on a microprocessor that, when frobbed, the processor will:
  • Set its registers to a predetermined state
  • Flush/clear any onboard cache
  • Discard pending interrupts
  • Jump to a particular (often hardwired) memory location.
Of course, each processor handles frobbing of its RESET line in a different way.

RESET can also be a button on a computer which will restart it; part of what this button does is usually frobbing the above-mentioned RESET pin.