Article: Press and hold the device-specific button combination while your phone is powered off. The buttons vary from device to device. Nexus devices - Volume Up, Volume Down, and Power Samsung devices - Volume Up, Home, and Power Moto X - Volume Down, Home, and Power Other devices generally use Volume Up and Power. Some devices with physical user interfaces may use the Power and Home buttons. Use the volume buttons to scroll through the menu options. This selects the reset option. This confirms your selection. This starts the reset process and reformats your Android device to its factory settings.

What is a summary?
Power off your device. Boot your phone in Recovery Mode. Scroll to Wipe data/factory reset. Press the Power button. Scroll to Yes. Press the Power button.