Abbreviation for Local Area Network. A LAN is a group of computers and associated devices that share a common communication line with each other. A LAN may be as small as one or two computers networked together in a home, or as large as thousands in a large organization. Typical LAN’s, as they are deployed in commercial installations, involve a server that provides access to resources for various clients or terminals around the facility. LAN’s are sometimes connected to a WAN (Wide Area Network, which is usually, but not necessarily the Internet) through a switch or some hardware that regulates the flow of data in and out of a facility.