A compensator is an attachment (sometimes integrated) on a gun barrel that allows gas to escape upward at the end of the barrel, creating a jet effect and reducing muzzle flip.
IMO this weapon is really underrated for /ra COR. Path B is currently the most accurate /ra weapon afaik. If snapshot uncapped then snapshot+10 and triple shot+10% is equivalent to haste +10% TA + 5% for melee TP since triple shot can be activated half the time.