Razer

While tracking, a typical mouse will send its X and Y movement calculations, as well as information about which buttons are pressed, to the computer 125 times a second (meaning once every 8ms). This is known as a polling rate and is expressed in Hertz. Most mice often have a polling rate of 125Hz.

Polling can be seen as how many times a device "reports" information to a computer. When a device reports information once to the computer in one second, its polling rate is considered to be 1 Hertz. So if a mouse or keyboard says that it has a polling rate of 125 Hertz, this means that the device is reporting information 125 times in one second. The more times a device reports to the computer, the faster the computer will process this information for use in applications or games.

The higher the polling rate, the more often the computer receives information about the status of your mouse and the faster the computer can respond to your command. For instance, if you were to use a mouse with a polling rate of 1 Hz for a FPS, your computer would receive movement date once every second, which would result in your on screen avatar in moving once a second.

A standard polling rate of 125Hz is seen to be adequate for use in normal computer applications as an eight millisecond delay is negligible when navigating a desktop. However, when playing a game and directing actions in a FPS, RTS or virtually any other genre of game, an eight millisecond delay can cause slightly delayed reactions that would make the difference between life or death, defeat or victory.