Actually, being a rather smart dude and having some sniper experience in my past, I think I understand these concepts quite well.
They are different concepts, but not completely so in that they interact with each other. I would say "chance to hit" is the final numerically stated result after determing all applicable factors. One of those factors, however, is the "accuracy" of the shooter (or wind, or distance, or the spin of the bullet itself, or the rotation of the Earth under a bullet as it travels a long distance). A skilled shooter (ie an accurate shooter) will have a higher chance to hit at longer distances. An unskilled shooter (ie an inaccurate shooter) will have a lower chance to hit at longer distances.
Basically, the accuracy of the shooter determines your overall chance to hit. That's why we can state that accuracy determines chance to hit.... because it does.
