A stance is a general combat strategy that you enter by using an action with the stance trait, and you remain in for some time. A stance lasts until you get knocked out, until its requirements (if any) are violated, until the encounter ends, or until you use a stance action again, whichever comes first. After you take an action with the stance trait, you can’t take another one for 1 round. You can enter or be in a stance only in encounter mode. You can Dismiss a stance.
Source: Player Core pg. 140
Requirements: You are wielding a ranged weapon
You take aim to pick off nearby enemies quickly. When using a ranged volley weapon while you are in this stance, you don’t take the penalty to your attack rolls from the volley trait. When using a ranged weapon that doesn’t have the volley trait, you gain a +2 circumstance bonus to damage rolls on attacks against targets within the weapon’s first range increment.