I did initially think that after I purchasing a sight or scope that I just install it and that's it, its done and wherever the dot or crosshair is pointing is what Im going to hit but it turns out that's not quite the case. You MUST zero it in. 

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Zeroing in a rifle scope refers to the process of adjusting the scope's reticle (the crosshairs or other aiming point) to align with the point of impact of the bullet at a specific distance. This allows the shooter to accurately hit targets at that distance without the need for holdover or compensation.

The process typically involves shooting a group of shots at a target set at a known distance, and then adjusting the scope's elevation and windage turrets (or knobs) to move the point of impact of the bullets to match the position of the reticle. Once the reticle and bullet impact are aligned, the rifle is considered "zeroed" at that distance.

Zeroing a rifle scope is an important step for any shooter looking to achieve accurate shots at different distances. It's important to know that the process is usually done at a specific distance, usually 100 yards for most rifle zeroing, but the distance can vary depending on the caliber, the ammunition and the purpose of the rifle. Once the rifle is zeroed, the shooter can use the reticle to estimate holdover or windage corrections for targets at other ranges, using the reticle's markings or ballistic calculators or reticle.