Point of Aim vs Point of Impact

There are a lot of things that can happen to a bullet on its way to the target. That's why, when sighting a target through a scope, shooters are comparing point of aim to point of impact. Simply put, when firing a bullet from over 600 yards, where you are aiming is not going to be where the bullet lands. All sorts of variables work on a bullet during its long flight to the target. Ideally, shooters want point of aim and point of impact to be the same. They line up these points with fine adjustments to the scope once range, heat, and windage have been factored into the shot.