When you restore something, you usually keep the structure the same, but you improve its appearance and possibly its functionality. For example, if you renovate a room, you can turn it back into a new one with structural changes, such as tearing down walls and altering its original design. However, if you restore it, you'll most likely focus on making it look better with aesthetic changes, such as painting it. The word renovate is also often used to describe second-hand technology that has been rebuilt to restore operation by replacing a component.
which has failed. There is a meaning in the OED entry for the noun restoration. See “Meaning and Use” for definition, usage and quotes.
