A VLAN, or Virtual Local Area Network, is a technology that allows network administrators to create separate networks within a single physical network. This means that devices can be grouped together logically, even if they are not physically located in the same place. VLANs help improve network efficiency and security by isolating traffic between different groups of users or devices. By using VLANs, organizations can manage their networks more effectively. For example, a company might create a VLAN for its finance department and another for its marketing team. This separation ensures that sensitive financial data is kept secure and reduces unnecessary traffic on the network, leading to better performance.