Aim allows you to bypass 1/2 AVThe numeric value representing how much damage armor absorbs... More with a Successful Spot.
Once per round, you may attempt to aim an attack that will hit a specific part of target. An aimed attack is DifficultYour skill is halved when a task is harder than average, whi... More by default. With a successful Heroic Action (Spot, Sense) you can aim, and your attack is at your standard skill rating.
An aimed shot can do one of two things: It may negate 1/2 AVThe numeric value representing how much damage armor absorbs... More of worn armor*. Or it can target a specific part of the body. This can have many effects, and it is up to the player and SG to determine the effect.
*Some creatures have natural AVThe numeric value representing how much damage armor absorbs... More, so bypassing it would only happen if they have known weak spots. AVThe numeric value representing how much damage armor absorbs... More is rounded up.