While some floors require complete sanding and refinishing, many can be refreshed by a process of screening and recoating. This is a process that takes off only the top coats of the old finish but does not remove any wood. A new, fresh coat of finish is then applied, bonding to the lower layers of the old finish.
Recoating is appropriate only if the floor is merely slightly scratched, the finish is not yet worn through, and it does not have a wax build-up that may interfere with the adhesion of the new finish. In cases of serious scratches or worn finish, consider refinishing instead.