Conex box in the context of Largest container shipping companies

An intermodal container, often called a shipping container, or a freight container, (or simply "container") is a large metal crate designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – such as from ships to trains to trucks – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. It is like a boxcar that does not have wheels. Based on size alone, up to 95% of intermodal containers comply with ISO standards, and can officially be called ISO containers. These containers are known by many names: cargo container, sea container, ocean container, container van or sea van, sea can or C can, or MILVAN, or SEAVAN. The term CONEX (Box) is a technically incorrect carry-over usage of the name of an important predecessor of the ISO containers: the much smaller steel CONEX boxes used by the U.S. Army.

Intermodal containers exist in many types and standardized sizes, but 90 percent of the global container fleet are "dry freight" or "general purpose" containers: durable closed rectangular boxes, made of rust-retardant weathering steel; almost all 8 feet (2.4 m) wide, and of either 20 or 40 feet (6.1 or 12.2 m) standard length, as defined by International Organization for Standardization (ISO) standard 668:2020. The worldwide standard heights are 8 feet 6 inches (2.6 m) and 9 feet 6 inches (2.9 m) – the latter are known as High Cube or Hi-Cube (HC or HQ) containers. Depending on the source, these containers may be termed TEUs (twenty-foot equivalent units), reflecting the 20- or 40-foot dimensions.