Steam mops usually do not use any other kind of cleaning solution other than water to clean. The steam loosens dirt and grime allowing the mop pad to wipe over and trap it. The steam also has an added benefit of disinfecting the floor.
Steam mops are great for many hard surface floor types, but may not be the best option on wood floors. Steam mops are more expensive than traditional mops, but the mopping pad can be washed and reused frequently.