There are three main types of computer networks: local area networks (LANs) which connect computers within a single building or small area; wide area networks (WANs) which connect computers over large distances using leased telecommunication circuits; and metropolitan area networks (MANs) which connect users within a region larger than a LAN but smaller than a WAN. LANs are usually confined to a single building, WANs are used by businesses and organizations to relay data worldwide, and MANs interconnect resources in an area like a city.