Polling rate is how often your mouse sends its position to your computer, measured in hertz — reports per second. At 1000 Hz the mouse reports once every millisecond; at 4000 Hz, every quarter of a millisecond; at 8000 Hz, every eighth of a millisecond.
What a higher rate changes
More frequent reports mean your PC always has fresher position data, which can make cursor and crosshair movement look smoother — most noticeably on high-refresh monitors and during fast movements.
What it costs
Every report is work for your PC to process, so very high polling rates use more CPU — and on a wireless mouse, more battery. Some older games and systems also handle very high rates poorly.
How to set it
Start at 1000 Hz; it's been the standard for years for good reason. If your mouse supports higher rates and your system stays smooth, step up and see whether you notice a difference. If you see stutter or the battery drains too fast, step back down.
Polling rate is one part of the picture — shape, weight and your mousepad matter at least as much. Browse mice and mousepads.