VSync is do eliminate screen tearing. Search for better explanation what these terms are standing for. It is just for a smoother experience. Your card tries to match your monitors refresh rate. But on games like Counter Strike:Global Offensive or other competitive and fast online games, this could be counter productive. Some are talking about no difference, but some (like me) see a quite huge difference. It is almost unplayable at 60 fps to me, maybe because the sync is forced. For other offline games, its mostly better with VSync on. But this is a question of taste and if your hardware works quite well with it.