A shipping line is like a big transport company that moves things, like toys or clothes or food, from one place to another place far away. They use really big boats, called ships, that can carry lots and lots of things all at once.
Just like how you have to plan ahead before going on a trip with your family, shipping lines also have to plan ahead before starting their journey. They have to decide which route they will take and how much stuff they can carry on their ship.
Sometimes, shipping lines have their own ports, which are special places where ships can dock and unload their cargo. They have to make sure that the cargo is safely taken off the ship and delivered to the right place.
In the end, shipping lines help people all over the world get the things they want or need, even if they are very far away.