what V-Sync does while active in a project?

grimm_

I've realized it has an option on menu to activate/deactivate the V-Sync in the project. what difference it does?

xyz

grimm_ It makes your game's frame rate same as monitor's refresh rate. In other words in synchronizes fps with monitor's vertical refresh rate. Hence vertical synchronization or vsync for short. The main benefits are saving gpu power by rendering only as many frames per second as can actually be displayed by the monitor, and not starting to render a frame in the middle of monitor's frame redraw which can cause "image tearing" artifacts. Google it for more details, there's plenty of articles around the web.

Toxe

And the immediate effect would be that without VSync your game (well, any game) would render as many frames as it can (for example a couple of thousands per second for 2D), whereas with VSync it's 60 FPS for most people.