Cargoes fall into two basic categories: liquid and non-liquid, termed wet cargoes and dry cargoes. Each type is carried in different ways for different reasons.

Dry cargoes fall into three main categories: conventional, containerised and roll-on/roll-off. A conventional cargo, sometimes referred to as breakbulk cargo, is one which is lifted on and off a ship one piece, or bundle, at a time by means of cranes or derricks, but not shipped on trailers or in shipping containers. Such cargoes are carried in conventional ships which, if operated on a regular basis between advertised ports, provide a conventional service. These ships are often of the tween deck or multideck type which not only allows them to carry safely cargoes having many different stowage requirements but also facilitates distribution in the ship of cargo for several ports of discharge. Conventional cargo is cargo which very often does not fit into or onto any of the standard shipping containers by virtue of its length, width or height. Such cargoes are termed uncontainerable or uncontainerisable.