WAN covers a wide geographical area which includes multiple computer or LANs. It connects computers through public networks, like telephone system, microwave, satellite link or leased line.
Most of the WANs use leased lines for internet access as they provide faster data transfer. leased line is a dedicated connection between service provider and consumer. The main advantage of using leased lines is that there is no interface by other users outside the network.
WAN helps an organization to establish network between all its departments and offices located in the same or different cities. It also enables communication between the organization and the rest of world.