LAN OR LOCAL AREA NETWORK:
A local area network (LAN) is a network that connects computers and other devices in a relatively small area, typically a single building or a group of buildings.
Most LANs connect workstations and personal computers and enable users to access data and devices (e.g., printers and modems) anywhere on the network. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.
LANs can be characterized by their topology, protocols and media. Topology is the geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line. Protocols are the rules and encoding specifications for sending data. They also determine whether the network uses a peer-to-peer or client/server architecture. The most common type of LAN is Ethernet. Media is what is used to connect the devices, i.e., twisted-pair copper wire, coaxial cables, fiber optic cables or radio waves.
LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line because of their short distances and the fact that they do not have to rely on copper wire media (with its limited capacity). However, the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.
Computers on a smaller LAN typically share the resources of a single server, which provides application programs and datastorage. Users who need an application can download it once and then run it from their local hard disk drive (HDD). They can order printing and other services as needed through applications that run on the LAN server.
A local area network may serve as few as one or two users (for example, in a home network) or as many as thousands of users (for example, in a large company).
LANs can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).
MAN OR METROPOLITAN AREA NETWORK:
A Metropolitan Area Network, or MAN, is a series of LANs (Local Area Networks) that are interconnected through various means in a Metropolitan area such as a city and its subburbs.
If a company has a few offices in the same city, and the computer users at each location are able to share data between the two offices, they are generally doing this over a MAN.
WAN OR WIDE AREA NETWORK:
Definition: A WAN spans a large geographic area, such as a state, province or country. WANs often connect multiple smaller networks, such as local area networks (LANs) or metro area networks (MANs).