means the monitor will simply output your game frames as screen refreshes. Atm you basically have for example 125 frames per second being output by the game itself to the gfx card buffer and a monitor refreshing for example every few 1/120hz=8.3 milliseconds showing the latest frame from the buffer. This aint that constant and a bit jittery with some tearing unless you use triple buffering(which causes extra delay on the other hand). But with that technology it will just refresh as soon as the new frame is rendered ~125 times per second meaning it will be smoother(like 9999999999999hz screen without tearing but the bottleneck is 125fps game cap) and more responsive(though it depends on nvidia implementation). The only bad part is that it's fairly hard to implement it with strobing backlight (for those who prefer lightboost).
tldr: Gonna be good, but simply raising fps cap to 250 or so would improve the game much more