VLAN's exists when multiple devices are grouped together and function as a separate entity. This is
mainly for the purposes of maintaining security between groups of the network. On the whole, a VLAN is very similar to that of a physical LAN. Their main difference is VLANs capability to group end stations together without the requirement of being located on the same network switch. In VLAN, configuration of the network can be done via software extensively. Basically, VLANs are used at layer 2 to break up broadcast domains.
Each VLAN is considered as a separate entity and it can only reach another VLAN through a router. You can use a single network with VLANs but when one network goes down for some reason, the entire logical network is concerned. VLANs are very useful when an IT professional (system or network admin) wants to group organization departments for better work performance, less traffic, and more efficiency.
