One of the pros will correct me on this if need be, but here's how I understand the basics of it...
1) Pin-to-PAP distance: Shorter rolls earlier, longer rolls later.
2) Pin-to-VAL distance: Shorter means quick transition, longer means longer transition.
Example: you can have a pin far away from your PAP, but closer to your VAL. Doing this means the ball will roll later, but when it does start to make its move, will make it abruptly. In other words, very snappy at the breakpoint.
This is the theory behind part of the "Tommy Jones" layout. You get the pin high above the fingers but close to the VAL, so when it transitions it makes a sharp move. I have a ball drilled this way (Dyno-Thane Threshold) and that's exactly the move it makes. There's also a MB component to the Jones layout.
Playing around with those two distances allows you to control your reaction characteristic at the breakpoint. If you have a MB ball, there's yet another element of control.
Jess