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. The very first thing that has to be done to put your device in recovery mode is turning it off.
2. Then wait few seconds and press and hold these buttons: Volume Down + Power + Home.
3. Now when you will see LG logo you can release the buttons.
4. If you did all steps correctly you should be seeing recovery mode menu.
5. Congratulations you are in Recovery Mode.