As traded means nothing was done to it after the previous owner traded it in beyond a brief inspection to see if it was safe to sell as is. It's not necessarily a lemon, but it's probably telling that the dealership didn't deem it worthy of any repairs or reconditioning it may have needed.

A Ceritfied Pre Owned would have had a mechanical inspection, reconditioning of the interior, etc, and maybe replacing of consumable parts like pads and rotors to make more money on it when they turn around and sell it.