An action point, commonly abbreviated AP, is a point in games to determine how much action a player, unit, or video game character can do in a single turn.
Within computer and video games they are predominantly used in the turn-based tactics genre. A major difference from hit points and magic points is that action points recover automatically over time in combat rather than with items as hit points and magic points are usually recovered.
Any action (in some cases including using items) consumes a certain amount of AP. A unit cannot execute an action if there's not enough AP. If the unit has zero AP, that unit's turn is over. The player however, may end the unit's turn early. When it is that player's turn again, AP is replenished. AP may be partially restored or fully restored, and in some games, restoration may bring the unit's AP over the maximum limit that unit normally has.
Using the turn-based tactics genre as an example:
To add a sense of realism, the more stressful the action is, the more AP is consumed. For example, in land based combat, having a character move over rugged terrain may consume more AP than moving over smooth terrain. Using more powerful attacks also consumes more AP. In the Front Mission series, using a shotgun consumes a different amount AP than using a sub-machine gun or a rifle.
Another idea of AP is to use it as a sort of stamina meter in real time combat games. In Star Ocean: Till the End of Time, a battle mechanic employs a stamina bar known as Fury. Attacking consumes Fury, and if the character does not have enough, he or she cannot attack. Standing still recovers Fury. In other games such as first-person shooters, a stamina meter may be used for actions such as jumping or sprinting. Normal actions won't affect the meter, apart from (sometimes) hampering its recovery rate (such as running after a sprint).