A Port is About Movement
The purpose of the port is to smoothly and efficiently move cargo from ships inland, and from inland carriers like trucks or trains to the port and onto ships. If everything is working well, ships moor, quickly offload their cargo, load new cargo and are on their way. In the same way, trucks and trains bring cargo to the cargo yard, quickly unload it, and efficiently load new cargo for inland transport to store, distribution centers, or other destinations.
The diagram shows the efficient movement of cargo from ships to the yard and onto inland transportation like trucks and trains. It also pictures the efficient movement of cargo from trucks and trains to the yard, and then onto the ships.