The term gunner described a person who operated weapon systems onboard armed vehicles or starships.
Typically stationed in a vehicle operated by multiple crewmembers, gunners controlled weapons that usually operated independently of the vehicle's pilot or, in the case of larger starships, the rest of the crew.
A gunner would either be in charge of all of a vehicle's weapons (like in the All Terrain Armored Transport), in split control of a vehicle's weapons with the vehicle's pilot (like in the T-47 airspeeder, Aleph-class starfighter, or Scimitar assault bomber), or in co-control of the vehicle's weapons along with one or more other crewmembers (like in a Skipray Blastboat or an Imperial-class Star Destroyer). The kinds of weapons that required independent gunners included rear-firing blaster or laser cannons, quad lasers and missile launchers. Gunners in capital-ship grade weapons emplacements such as heavy turbolaser batteries and ion cannons almost always operated as part of a larger weapons crew.
Gunners served on many types of vehicles including walkers, military landspeeders and airspeeders, starships of all sizes, and ground-based turrets of all types, including anti-vehicle and anti-personnel emplacements. Those serving as gunners, both in a civilian and military capacities, often went through special simulator and live-fire training in order to become certified in the operation of their weapon of choice and to improve their skills.
Those notable for their skill as gunners included Han Solo and Wes Janson, along with many Jedi Knights such as Saba Sebatyne, Leia Organa Solo, Luke Skywalker, and many others. It was through their use of the Force, which allowed them to sense the intentions of the enemy, that gave them a distinct edge over their opponents, particularly when dealing with enemy starfighters while manning small-scale anti-ship weapons.
Among the ranks of the Alliance to Restore the Republic, the rank of True Gunner was the highest order of gunnery awarded to those who displayed superior abilities. Lieutenant Janson earned his True Gunner's insignia during his early days of service to the Rebellion.