A button or switch on many computers that allows you to reset the computer. When you press the reset button, the computer will enter its start-up procedure as if you had turned the power off and then on again. Generally, you would use the reset button only when a program error has caused your computer to hang.
Note that on PCs, pressing the reset button is somewhat different from performing a warm reboot by pressing the Ctrl +Alt+Del reboot keys. Pressing the reset button performs a cold reboot. When you perform a warm reboot, the system does not repeat the initial start-up stages during which memory is checked.