A ship, also known as a freight ship, is a large watercraft that travels the oceans and other waterways to transport passengers and goods as well as specific tasks like defense, research, and fishing. Ships were originally sailing vessels with at least 3 square-rigged masts and a full bowsprit. Ships have made their impact in history as they have supported both human migration and commerce. Ships are differentiated from boats by their size, shape, and load capacity. Freight ships are designed specifically for their task, and are typically equipped with cranes to help load and unload cargo. Ships are constructed in all sizes and generally have a life expectancy of 25 to 30 years.