The Revert command reopens the last saved version of the file, abandoning changes that have been made since the file was last saved. Don't like the way something is turning out? Or maybe that last filter you applied made what was once a beautiful piece of art into an unfortunate mess. Simply choose FileRevert or use the handy F12 keyboard shortcut to restore your document to the way it looked when you last saved it. It's kind of like Photoshop's panic button.
One of the nice things about the Revert command is that it too is undoable, just in case you change your mind. As if you weren't already given enough second chances.