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. For a start take your phone and hold down your power button to shut it down.
2. Then press volume down button and power button and hold them untill next step.
3. Now when you see LG logo, release the keys before the logo disapears.
4. Now you will enter recovery mode screen.
5. This is the end if you want to know how to switch between options use volume keys and to proceed use power button
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.