Your computer can communicate with another computer down the street, across town, across the country and across the world, thanks to a vast array of networks. The World Wide Web is a system of interconnected information sources, however, it would be meaningless without networks that allow computers to access information and communicate with each other.
A local area network, or LAN, is a connection of computers within a small area, such as an office, a building or multiple buildings located close together. Local area networks can be as broad as connecting computers within a college campus, or as simple as linking two computers in a household. A LAN is relatively inexpensive compared to other types of network applications, and can be built with wired or wireless connections. Local area networks operate within a modest geographical area, but by connecting to other larger networks, a LAN's reach is greatly expanded.
When two or more local area networks are connected together it is known as metropolitan area network, or MAN. Many LANs within a city are often linked to a MAN through very high speed connections, such as fiber optic cable. In many cases metropolitan area networks are operated by a government entity, or a large company, such as a cable TV provider, that make services available to a city and suburbs. In many instances, metropolitan area networks are important links between the smaller, localized LAN, and the vast coverage of a wide area network.
A wide area network, known as a WAN, covers broad geographical areas, like a state, a region or entire country. A WAN can be self-contained, but almost always connects with other local and metropolitan area networks. Wide area networks utilize networking equipment that is very costly and are mainly operated by large corporations or communications companies that need to share data over a vast area. As an example, a large retail drugstore chain would use a WAN for customer prescription information. A customer can then fill a prescription at one location, and through a wide area network, that information can be accessed for a refill at any location the retailer has worldwide.
Storage area networks, called a SAN, are a variation of a LAN. The main purpose of a SAN is the storage of large amounts of data that can be retrieved at a high rate of speed. Storage area networks are commonly used by businesses that maintain broad databases. Media companies that perform large amounts of video editing benefit by using storage area networks because of their high data transfer rates.