A VLAN (Virtual Local Area Network) is a technology that allows network administrators to create separate networks within a single physical network. This helps improve security and performance by segmenting traffic, so devices in one VLAN cannot directly communicate with devices in another VLAN without proper routing. VLANs are commonly used in organizations to group users by function, department, or project, regardless of their physical location. This flexibility simplifies network management and enhances resource allocation, making it easier to control access and optimize bandwidth usage across the network.