What does it for? In the past, a phone is more of a device used to make calls or text. However, it's much more than that.
Most Android devices are now defaulted with a fairly simple Recovery mode with features like Reboot System Now, Apply Update from ADB, Apply Update from External Storage, Wipe Data/Factory Reset, Wipe Cache Partition, Apply Update from Cache.
Just like a lot of other things with Android, even the Recovery Mode can be customized to do more things.
1. The whole operation start from turning off your device, so hold down your power button to turn it off if its on.
2. Next step is pressing combination of three buttons and holding them down. So press Volume down + Power buttons.
3. Hold them untill you see LG logo and wait few seconds.
4. Now you should see Recovery mode menu, good job! To move highlighted area here use volume buttons "+" is for up and "-" for down, and to confirm press Power button.
Recovery is included on a separate partition from the main Android OS on all Android devices.
You can boot directly into recovery mode and use it to factory reset the device, delete the cache partition, or apply software updates.
It can help you fix your device.