Ever make a mistake while typing? Yeah, I know, we never do that! Would you like to be able to go back and undo it so your mistake is long gone? If this sounds good, all you have to do is hit Ctrl + Z on your keyboard.
Using Ctrl and Z at the same time will undo any changes you've made (good or bad). Maybe you've done something and it's not necessarily a mistake, but you would like to redo it. Well, just use Ctrl + Z and it will be taken away! This undo shortcut works in just about any program.
You can also undo by going to Edit, Undo, but the keyboard shortcut is much faster and easier!