In the SPECIAL character system, perks are bonuses the player character can pick up when gaining a level. The number of ranks each perk has determines how many times the perk can be taken. In contrast to traits, perks are purely beneficial.
A character's perk rate determines how often the player gets to choose a new perk (or an additional level for an already obtained one). In Fallout, Fallout 2 and Fallout Tactics the player can choose a perk every three levels, with Fallout Tactics offering different rates for non-human characters. In Fallout 3 and Fallout: Brotherhood of Steel, the player gets to choose a perk (or "skill") at every level-up.
Please refer to the overview pages linked on the right for an overview of perks per game or to Category:Perks for an alphabetical listing of perks in the Fallout games.