G-SYNC & FreeSync (Adaptive Sync)
Adaptive sync lets the monitor vary its refresh rate to match the GPU's output, removing screen tearing without forcing you to cap frame rate.
Without it, the monitor refreshes on a fixed schedule while the GPU finishes frames whenever it can. When a new frame arrives mid-refresh, you see tearing — the top and bottom of the screen showing different moments in time.
Adaptive sync inverts the relationship: the display waits for the GPU. NVIDIA's implementation is G-SYNC, AMD's is FreeSync, and many modern monitors are certified to work with both.
It helps most in the range where frame rate fluctuates, which is nearly all real gameplay. Even a system averaging high frame rates dips during demanding scenes, and those dips are exactly where tearing appears.