Fighters are single-pilot combat small craft. They are lightweight enough that they can be economically fitted with powerful element zero cores, making them capable of greater acceleration and sharper maneuvers than starships.
Kinetic barrier shields changed starship battles from short, vicious bloodbaths to extended, indecisive slugging matches. Only the main gun of a dreadnought could punch a mass accelerator slug through the barriers of an opposing dreadnought. This changed with the development of the fighter-launched mass disruptor torpedo, a short-ranged weapon that can penetrate kinetic barriers to destroy their projector assemblies.
Starship GARDIAN defenses must be overwhelmed through swarm tactics. Fighter groups can take heavy casualties pressing their torpedo attacks home. Once fighter-launched torpedoes have crippled an enemy's barriers, the mass accelerators on frigates and cruisers can make short work of them.
Interceptors are a type of fighter optimized to attack other fighters, with no ability to damage starships. Interceptors are used to screen friendly units from incoming fighter attack.