A hard reset, also known as a factory reset or master reset, is the restoration of a device to the state it was in when it left the factory.
All settings, applications and data added by the user are removed.
The term is often heard in reference to smartphones and tablets but laptop and desktop computers, as well as most other electronic devices, can usually be restored to factory conditions.
1. First step here that you should do is switching off your device.
2. Wait 10 seconds and press and hold combination of those buttons: Volume down + Home + Power.
3. Do not let go untill you see LG logo on the screen.
4. After that, your phone will be in recovery mode.
5. To navigate use your volume buttons and power button to select an option.
6. Now go down to wipe data/factory reset option and select it.
7. And this is it! you have finished the entire process.