A ship is a large craft that floats and moves on water. Today there is no hard and fast rule for separating ships and boats. In the past a "ship" was a sailing vessel with at least three square-rigged masts and a full bowsprit. Ships in general are designed to carry very large amounts of cargo or passengers. Worldwide there are about 100,000 vessels registered as ships.

Ships have been needed since ancient times. Many countries had to defend themselves, and so needed ships that could carry armies. These were warships. When cannon were invented, warships carried banks of cannon along each side. Those are, for example, marked by the holes on the side of the sailing ship in this picture.

Ships have also been needed to carry people and cargoes. Early ships were small and used single sails. They were easily swamped by storm waves and gale-force winds, and so stayed quite close to the shore. That is, for example, why the early European explorers went from Portugal down the coast of Africa, then along the coast of Asia until they reached the Spice Islands (now part of Indonesia). They were simply afraid to make ocean crossings, and also they did not have accurate ways of navigating out of sight of land.

Gradually, ships became bigger and had several masts. Compasses were invented. It was at this time that it was possible to cross the oceans and explore other parts of the world.

Because ships float, their weight is taken up by the water below them. It is called buoyancy. There is very little friction between the ship's hull and the water compared to, say, train wheels on tracks and truck wheels on roads. As a result, it needs less force to move them, and so they are cheaper. The downside is that they move more slowly than trains or trucks. But they are the only way of carrying large amounts of goods between continents, and so are vital to everyone on the Earth.

In the past, goods were put into ships holds one by one, using dockers and cranes. But in the 1960s containers and container ships were invented, so that ships could load and unload containers. This made loading and unloading cheaper and faster. It is the main way in which goods are moved today. A container ship may carry a cargo over thousands of containers.