Networks can be classified according to their size, how they are wired together, what they do, and how they communicate.
Types of networks, by size
Local Area Network (LAN)
Computers networked together in a self-contained group form a Local Area Network, or LAN. A LAN typically is contained within a single building or a group of neighbouring buildings. Two computers linked together at home are the simplest form of a LAN. Several hundred computers cabled together across several buildings at school form a more complex LAN. LANs are usually connected with coaxial or CAT5 cable.
Metropolitan Area Network (MAN)
A Metropolitan Area Network is a network that interconnects computers in a geographic area larger than that covered by even a large LAN but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network, and it also is also used to mean the interconnection of several local area networks by bridging them with backbone lines. Several branches of a chain store within a city might find a MAN useful. MANs are usually connected with fibre-optic cable, microwave transceivers or leased data landlines.
Wide Area Network (WAN)
A WAN is geographically large. It is often formed by the joining together of LANs in distant places. A national banking organization, for example, may use a WAN to connect all of its branches across the country. The difference between LANs and WANs is getting blurry as fibre optic cables have allowed LAN technologies to connect devices many kilometers apart. WANs are usually connected using the Internet, ISDN landlines or satellite.