When does infield fly rule apply?

If there are less then 2 outs and runners on 1st and 2nd or the bases are loaded. If a ball is popped up on the infield in fair territory the umpire will call "Infield Fly", the batter is out, and the runners are not required to advance, but can do so if they determine at their own risk of being safe or out. The ball is still a live ball in play, and it does not matter if the ball is caught or not.

The infield fly rule does not apply to bunted balls that are popped up