With a Tag VLAN, the VLAN is assigned to a specific port. All users of the port must be members of the same VLAN.
VLANs simplify network management. A single connection can be used to manage multiple VLANs – physical location is irrelevant. Accidental crossover of data from one VLAN to another is simply not possible. Plus, reconfiguring a VLAN is an easy software solution, versus changing wired connections on a regular LAN.