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. 146
Your shots become nimble and deadly. While you’re in this stance, your ranged Strikes don’t trigger Reactive Strike or other reactions that are triggered by a ranged attack.
Special If you have Reactive Strike, you can use it with a loaded ranged weapon you’re wielding. The triggering creature must be within 5 feet of you for you to do so.