breakbulk is basically any cargo that is not in a container, and cant be poured. Heavy Equipment, telephone poles, Bags of Nickle Sulfate, locomotives are all examples of breakbulk cargo, and can be carried in general cargo ships.
Nirint makes a regular run to and from Cuba. the HC Melina is carrying containers, but also bags of Nickle Concentrate in bags in her hold. these bags get unloaded from the ship, then onto railcars for points west.
Holds typically do not have container guides, and containers can only be carried on deck. Also usually the full hold can be opened. These vessels may or may not have cranes, and are typically in the 100-150m in length range.
(Above) Capri ( and several other Vessels) frequently deliver rails for CN.
(below) Freisan Spring Loaded telephone poles
(Above) SE Veridian Delivered Windmill Components.
(Below) Flintermar Loading Wood Pellets.