Recovery, in Android, refers to the bootable partition, in which the recovery console is installed.
It contains tools to help repair your installations as well as install official OS updates by using a combination of key presses or instructions from a command line sometimes.
Android is open, meaning the recovery source code is available, so that building a customized ROM is relatively easy.
1. Start from turning off your device by holding down power button.
2. Wait 10 seconds and press and hold power button with volume down button and home button together.
3. When the screen will show LG logo, you can let go off the buttons.
4. After few seconds your phone will boot into recovery mode, congratulations.