I noticed when restringing my Grestch Electromatic Hollow Body guitar today that at the bridge there are some screws that alter the position of where the gap is where each string actually crosses over the bridge. Could someone tell me why this is so and what difference does it make which regards to the positioning of where the string crosses the bridge?

Here is an image of what I mean:


I hope this question makes sense!

They let you adjust your guitar's intonation so that it stays in tune along the entire neck. Turning those screws shortens/lengthens the string. It's good to check/adjust your intonation after switching string gauges, as that's a factor that could throw your intonation off.