LAN stands for Local Area Network. It's a group of computers which all belong to the same organization, and which are linked within a small geographic area using a network, often with the same technology (the most widespread being Ethernet).
A local area network is a network in its simplest form. Data transfer speeds over a local area network can reach up to 10 Mbps (such as for an Ethernet network) and 1 Gbps (as with FDDI or Gigabit Ethernet). A local area network can reach as many as 100, or even 1000, users.
By expanding the definition of a LAN to the services that it provides, two different operating modes can be defined: