You might actually need to use it on your device one day ...

Resetting an Android phone or tablet can be done using its settings. So if you're selling your phone, or giving it to a new employee, you can erase all of its data, including apps and settings ...

Resetting your Android device to factory settings erases all data on the device and clears out unnecessary files. The reset process wipes all your information from it, including private data, messages ...