Networks

The word network describes two or more computers that can share resources. These resources include printers, other computers, data, applications, communications, and just about anything else.
There are three basic types of networks
LAN - LAN stands for Local Area Network. These are networks that are limited to a specific, relatively small area. Usually this is just a single office, warehouse, building or even an apartment. Generally a LAN does not exceed the boundary of a single building and the connections between computers is permanent.
WAN - A WAN is a Wide Area Network. In many cases, a WAN consists of multiple LANs or MANs. A WAN can be huge (even covering the entire planet or extending out into space), and the connections between computer may or may not be permanent.
MAN - This stands for Metropolitan Area Network. The term is not used very much, and it is really just a variation on the WAN concept. You can think of a MAN as a WAN that is totally contained within the boundaries of a single metropolitan area (a city).