Input lag
The time between pressing a button and seeing the result on screen, summed across every link in the chain.
No single component owns the delay. The controller is polled at intervals, the game may not read it until the next pass of the game loop, the driver queues finished frames, vsync and triple buffering add waiting, and the display itself may spend tens of milliseconds processing the image. At 60 frames per second, every extra frame in the queue costs just under 17 ms.
The countermeasures each target one link: a TV's game mode switches off picture processing, variable refresh rate such as FreeSync removes the wait for vsync, and NVIDIA Reflex (2020) keeps the render queue short. Emulators went furthest with "run-ahead", which quietly simulates a few frames ahead and shows that instead. Fighting-game players measure it with high-speed cameras; everyone else just notices that something feels sluggish.