VLANs provide a means to segregate your network into distinct groups or domains. They also provide a means to prioritize the network traffic into each of these distinct domains. For example, a network may have a Voice VLAN and a Data VLAN. Grouping devices that have a set of common requirements has the following advantages:

The networking standard that describes VLANs is IEEE 802.1Q. This standard describes in detail the 802.1Q protocol and how Ethernet frames get an additional four-byte tag inserted at the beginning of the frame. This additional VLAN tag describes the VLAN ID that a particular device belongs to and the priority of the VLAN tagged frame. Voice and video traffic typically get a higher priority in the network as they are subject to degradation caused by network jitter and delay.