A VLAN is a switched network that is logically segmented, by functions, project teams, or applications rather than on a physical or geographical basis. For example, all workstations and servers used by a particular workgroup team can be connected to the same VLAN, regardless of their physical connections to the network or the fact that they could be intermingled with other teams. VLANs are used in order to reconfigure the network through software, so that devices or wires do not have to be physically unplugged and moved.
A VLAN can be thought of as a broadcast domain that exists within a defined set of switches. A VLAN consists of a number of end systems, either hosts or network equipment (such as bridges and routers) that are connected by a single bridging domain. The bridging domain is supported on various pieces of network equipment, such as LAN switches, that operate bridging protocols between them with a separate group for each VLAN.