Measures the gap between the screen turning green and your click, five times over, and reports the median. Browser and display latency are part of the number, so it is best used to compare runs on the same device.
Clicking before the signal voids that try and repeats it — that filters out anticipation from counting the rhythm.
The headline figure is the median rather than the mean: one lapse in five tries drags a mean a long way.
Simple visual reaction is usually reported around 200–250 ms. On the web, browser event handling and display latency add tens of milliseconds, so a slightly slower figure here is normal.
Usually yes — physical buttons on a mouse or keyboard beat a touchscreen. Compare grades between runs on the same input method.
Yes. A higher refresh rate and faster response mean the signal reaches your eye sooner. This number measures your device as well as you.