LAN stands for Local Area Network. A LAN consists of a group of devices in the same broadcast domain. For example all devices on one switch would belong to one LAN. All devices on a separate switch would belong to another LAN. Separate LANs are good for security and to maintain efficiency of the network. But this means that you would need a separate physical switch everytie you wanted a separate LAN. This is where VLAN comes into play. VLAN stands for Virtual Local Area Network. With VLAN you can have one physical switch that is logically separated into different LANs. Although there may be many devices connected to the same switch, devices on one LAN can only see devices that belong to their LAN. One switch can act as if it were multiple switches.
The advantage of VLANs is that it decreases cost and simplifies the administration of having multiple switches on the network.
