A LAN (local area network) is a group of computers and network devices connected together, usually within the same building. By definition, the connections must be high speed and relatively inexpensive (e.g., token ring or Ethernet). A Wide Area Network (WAN) spans over multiple geographic locations, which is composed of multiple LANs.
routers and switches
Routers and switches are both computer networking devices that allow one or more computers to be connected to other computers, networked devices, or to other networks. The functions of a router, switch and hub and are all different, even if at times they are integrated into a single device
Computer networking is an engineering discipline that aims to study and analyze the communication process among various computing devices or computer systems that are linked, or networked, together to exchange information and share resources.
In telecommunications, structured cabling is building or campus cabling infrastructure that consists of a number of standardized smaller elements (hence structured) called subsystems.