Networks come in all sizes and shapes. In fact, it’s common to categorize networks based on the geographical size they cover, as described in the following list:
Local area networks: A local area network, or LAN, is a network in which computers are relatively close together, such as within the same office or building.
Note that the term LAN doesn’t imply that the network is small. A LAN can, in fact, contain hundreds or even thousands of computers. What makes a network a LAN is that all those computers are located within close proximity to each other.
Usually a LAN is contained within a single building, but a LAN can extend to several buildings on a campus — provided the buildings are close to each other (typically within 300 feet of each other, though greater distances are possible with special equipment).
Wide area networks: A wide area network, or WAN, is a network that spans a large geographic territory, such as an entire city or region, or even an entire country. WANs are typically used to connect two or more LANs that are relatively far apart. For example, a WAN may connect an office in San Francisco with an office in New York.
Again, it’s the geographic distance, not the number of computers involved, that makes a network a WAN. If the office in San Francisco and the office in New York both have only one computer, the WAN will have a total of two computers but will span more than 3,000 miles.
Metropolitan area networks: A metropolitan area network, or MAN, is a network that’s smaller than a typical WAN but larger than a LAN. Typically, a MAN connects two or more LANs that are within the same city but are far enough apart that the networks can’t be connected using a simple cable or wireless connection.