High sustained damage, mediocre to zero mobility, mediocre burst (COMPARED TO ASSASSINS AND MAGES ONLY), mediocre to zero CC, average-high tankiness and most of all (this is the big part): has to build damage to get damage and has to build tanky to be tanky.
Usually separated, as Nacho said, into Juggernauts, Light Fighters and Heavy Fighters.
Juggernauts have relatively high sustained damage as "sustained burst" (with cooldowns in between), are very tanky, have weak CC and zero mobility. You are not supposed to facetank them, you are supposed to kite them since they WILL win 1v1s where you just stand there and auto each other.


Light fighters have very high (almost ADC level) sustained damage as autos, are not very tanky (but still moreso than most mages and assassins), moderately mobile though not as much as assassins and have zero or weak CC. You are supposed to CC them and burst them since most of their defenses comes from maneuvering and flanking the sides of the battle.

Heavy fighters have decent burst, decent sustained damage, decently tanky and moderately mobile though they do not excel at anything. They do, however, have significant CC which is used for either locking down priority targets or starting a fight with AOE CC. Depending on how they build you can either facetank them and beat them 1v1, CC them and burst them, or kite them.

The role of a fighter is to serve as the secondary DPS source on a team next to the ADC and a secondary tank on the team next to either a dedicated full tank or a support. If there is no primary tank, often a heavy fighter or juggernaut will build full tank or only 1 damage item and become the team's main engage.