You can deploy VLANs if you need to do the following:
Create a logical division of workgroups.
For example, if all hosts on a floor of a building are connected on one switch-based local network, you could create a separate VLAN for each workgroup on the floor.
Enforce differing security policies for the workgroups.
For example, the security requirements of a finance department and an information technology department are quite different. You can create a separate VLAN for each department and enforce the appropriate security policy on a per-VLAN basis.
Reduce the size of broadcast domain and improve network efficiency. You can split workgroups into manageable broadcast domains.
For example, in a broadcast domain consisting of 25 users, if the broadcast traffic is intended only for 12 users, then setting up a separate VLAN for those 12 users can reduce traffic and improve network efficiency.