Network VLAN switches are very popular and widely implemented in larger businesses and corporations. VLANs have the ability to group computers and network devices into their own common workgroup. These provide network user security and separate network functions common to the group. This also allows for separating network traffic for better bandwidth utilization. Also provides for priority traffic handling and isolating traffic that it using legacy or incompatible protocols.
VLANs can also duplicate company work groups over large or distant geographical areas. So workers in California and workers in New York would see the same network devices available to each group no matter where the worker is located. This provides easy transitions for workers or travelers between locations.
Data trunking for all work groups allows the transmission of trunked data over leased lines between geographic areas. (Trunked lines are lines that contain all the VLAN traffic.) The VLAN devices are then able to separate the trunked data back into separate company work groups. A problem using VLANs results when different workgroups need to communicate or receive data or mail from a common server. A router is needed to connect workgroups together or to connect workgroups to a common network device or common server.
VLANS or VLAN switches could also be used to provide Internet access for visitors with minimal network access. This provides needed Internet access for visitors and safety and security of company data and network drives. Also VoIP phone data can be prioritized and kept on its own VLAN to help provide better bandwidth for voice communication and prevent congestion of normal company data traffic.
The Computer Network Training website has additional information that you might find useful.