Tearing is what happens when your display doesn't keep up with your graphics card; the display shows part of 2 (or more) frames at the same time on different parts of the screen. VSync is used to remedy this issue, but that will lower your framerate.
Depending on what games you're playing, if you use a 770 with a vg248qe, you may not always be able to get the full benefit of the monitor, but it will certainly be smoother than with a 60Hz monitor, and have less (or no) tearing.