What it means
A clean title means the state title has no brand on it. It does not mean the car was never damaged: an accident that was not declared a total loss, or a repair paid out of pocket, leaves the title clean. At Copart and IAAI you will see clean-title cars from dealers, rental fleets, banks and insurers that recovered a stolen car.
What it means for a buyer
A clean title is easier to register and usually worth more, both in the US and abroad. Still check the auction damage, photos and history: a car can sit at a salvage auction with fresh damage and a clean title, because the brand is only added after the paperwork goes through.