There are plenty of different container depending on the goods that they are transporting, and whether they require full refrigeration.
For building purposes it is worth purchasing a refrigerated or insulated as this can affect the internal size of the unit you buy.
Containers with integrated refrigeration units with built in compressor/condenser will have slightly reduced length internally.
Containers that plug into to a mobile refrigeration unit (also called a clip on refrigeration unit) are a standard size internally. These containers are known as porthole containers as they have distinctive porthole openings on the outside for input and output connections.
Containers that are highly insulated but do not have connections for refrigeration.
Insulated containers can have various types of insulation which will affect the price and the R value.
Keep in mind that refrigerated and insulated units are much heavier due to the extra weight of the insulation and interior skin.