A factory reset, also known as master reset, is a software restore of an electronic device to its original system state by erasing all of the information stored on the device. A keyboard input button factory reset is used to restore the device to its original manufacturer settings. Doing so will effectively erase all of the data, settings, and applications that were previously on the device. This is often done to fix an issue with a device, but it could also be done to restore the device to its original settings. Such electronic devices include smartphones.
Since a factory reset entails deleting all information stored in the device, it is essentially the same concept as reformatting a hard drive. Pre-installed applications and data on the card's storage card (such as a microSD card) will not be erased. A factory reset effectively destroys all data stored in the unit.
Factory resets can fix many chronic performance issues (i.e. freezing), but it does not remove the device's operating system.