A local area network, or LAN, is a network of connected computers in a room, building, or set of buildings. These networks have been around since the beginning of computer use. A LAN is defined as a user network whereby data is sent at high rates between people located relatively close to each other. They do not usually make use of leased communication lines, but only use a means of communication that is provided by the installer of the network.
The Internet is a wide area network, or WAN, which is distinct from a LAN. In contrast to the term Internet, local area networks are often called intranets, though sometimes this term refers to a cluster of LANs associated with a particular company or organization but not connected to the larger Internet. This type of network uses a hub or router to connect computers together, typically with an Ethernet cable or wireless WiFi® technology. These technologies offer data transfer rates running between 10 to 10,000 Mbit/s.
Larger, more important LANs have redundant lines or other backup protocols. In networked computers, the most popular communication protocol is TCP/IP. Smaller LANs may be temporary and used between friends to play computer games over the network. Users can share files, view files, make changes to data on other computers if permitted, play movies or music on multiple computers at once, chat with instant messaging, send emails to each other, play games, and so on. All the advantages of the Internet apply, although they only include others on the LAN, and the data transfer rates are high.
Perhaps the most frequently employed use of a LAN is to connect users to the Internet with only one connected router. In modern times, people often use broadband cable or DSL modems to connect to the Internet, and it would be clumsy to have a modem associated with every computer. It's typically more efficient to plug the modem into a router and link the router to several computers with Ethernet cables. Configuring a LAN can be intimidating at first, but contemporary operating systems have programs that do most of the necessary configurations automatically, so setting one up is pretty easy.