MOA stands for Minute of Angle. It's a unit of angular measurement that defines the size of the red dot and its coverage on a target.
In practical terms, 1 MOA is roughly equivalent to 1 inch at 100 yards. Therefore:
A 2 MOA dot will cover 2 inches of a target at 100 yards, or 1 inch at 50 yards.
A 6 MOA dot will cover 6 inches at 100 yards, or 3 inches at 50 yards.
How to choose: A smaller dot (like 2 MOA) is excellent for precision shooting at longer distances as it won't obscure small targets. A larger dot (like 6 MOA) is ideal for close-quarters, fast shooting (e.g., on a pistol) because it's easier for your eye to pick up quickly.