A car with a reconditioned title is usually one that has been in an accident or other serious incident that resulted in the car being classified as a total loss by an insurer. Some states call this a "salvage" title.
Not all cars with a reconditioned title have been damaged, however. In some states, insurers classify recovered stolen cars as reconditioned if the owner has been compensated, whether the car is damaged or not. Additionally, many classic cars that have been extensively rebuilt have a reconditioned title.
In order for a car to get a reconditioned title, it must pass a safety inspection before it is road-legal. Most states also require dealers to disclose whether a used car they are selling is a reconditioned car.