There are two pin distances commonly seen on this website. Pin-to-CG and Pin-to-PAP.
When you see a range like 2-3", they generally mean pin-to-CG distance. (pin-out) This tells you how offset the core of the ball is in the center of the ball. While their are some subtle changes in reaction, the biggest issue with pin-to-CG is drilling options. Balls with short pin-to-CG distances aren't as versatile when attempting more exotic drillings.
The other distance talked about with the pin is pin-to-PAP. This is a drilling layout issue that is a major factor in the shape and amount of hook.
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Good luck & good bowling