To redo something is to do it over again, or to decorate it in a new way. You might redo your nail polish if the old layer is chipped, or redo your grandparents' living room if they're tired of the same old decor.
Thank goodness for second chances! Whenever you start over on a project from the beginning, you redo it: "I painted over that self-portrait, because I want to redo it." Or, you might redo your English essay if you bombed the first draft. The word redo is most often used in terms of renovating a space: "Let's redo your kitchen! We can paint the cabinets and use that big piece of marble for the countertop."