NVIDIA

Credit: NvidiaG-Sync monitor explained

Nvidia G-Sync is a type of adaptive sync technology for displays, namely PC monitors and gaming laptop screens. The feature helps displays tearing, tearing, and judging when you're gaming, particularly at high framerates. G-Sync only works when the display is connected to a PC using a compatible Nvidia graphics card.
Screen tearing is an unwelcome effect on the image's display when gaming (see photo above). It is the result of the game's framerate (the rate at which image frames are displayed) not matching the monitor's refresh rate (the frequency at which the display is refreshed). G-Sync fights this for refresh rates up to 240Hz, depending on the monitor; however, for displays with 4K resolution (aka UHD), that number drops to 144Hz (aka UHD). Tearing is a result of the graphics card outputting images at a faster rate than the monitor.
G-Sync works by matching the display's refresh rate to your Nvidia graphics card's render rate, so you see images right when they're rendered, while also fighting input lag. The feature also includes options for variable overdrive, which predicts when the next frame will eat and adjusts the monitors overdrive to fight ghosting artifacts. by Scharon Harding