Hi... i am not the best to explain this but in my reduced knows...
Vettical sinc will sincronized the game fps with your monitor refresh rate, on ots value or multiplos or sub multiplos.
In example, if you monitor have 60 hz, your video crad will attempt to maintain 15, 30, 60 120 fps.
In example, if you control room has 110 fps with vertical sinc off, if you turn it on, you will have only 60 because 110 do not reachs 120.
It is good to save computer resources for another videeo card funcions as particles or some thing.
But... always is a "but", if into the external view you have in example 27 fps, wich is enough to human eyes, but it do not reach 30 fps, then they will be reduced to 15 fps, wich is not good for human eyes.
Do not take it as true, is only just what i know about this....
