The most basic kind of network is a local-area network (LAN), which connects computers in a single office or building. A wide-area network (WAN) is two LANs linked together or a large interconnected collection of computers and other devices scattered in different locations.
Client/Server Networks
Most networks today use dedicated computers (servers) to act as a central repository of information for the other computers on the network. This type of network is called a client/server network. The server houses data, "serves" it up when users on the network request information, and performs centralized tasks such as backups and printer and modem sharing.
Peer-to-Peer Networks
LANs without dedicated servers are called peer-to-peer networks. These configurations bypass the need for a server by connecting computer workstations and peripherals directly to each other. Peer-to-peer networks are less expensive than client/server networks but do not offer the same level of central control and security.