Transportation is the movement of goods and people from one place to another. It is important because it enables communication, trade, and the establishment of civilizations, though it can also cause pollution. There are two main types of transportation - economies of scale, which provide cost savings through increased production, and economies of distance, which decrease costs per unit as distance increases. Key participants in transportation decisions include shippers, who are responsible for shipments; consignees, who are financially responsible for receiving shipments; carriers, who deliver shipments; governments, who build infrastructure and regulate transportation; and the public, for whom transportation systems aim to serve.