Very basically, refinishing hardwood floors will take away the first layers of the wood to reveal the untouched wood underneath. This wood can then be sealed and look like brand new hardwood floors. Removing the top, damaged layers of wood leaves the floor looking refreshed.
Refinishing hardwood floors is a great option for flooring that looks old and worn, but not terribly damaged. However, the refinishing process can be long and tedious, especially if it is done by someone who has never done it before.