Box Truck
Box vehicles usually have a rectangular cargo space. Outside of the actual cab and unreachable from the cab itself, the cargo area is on a frame.
Dry Van
Dry van trailers are used to transport goods while shielding them from the environment and traffic hazards, as they are usually completely enclosed.
Reefer
Reefer is slang for any trailer equipped with an auxiliary refrigeration unit. This is the most common way for transporting frozen or chilled items.