A VLAN, or Virtual Local Area Network, is a logical network segment built on top of physical switching hardware. Devices in different VLANs are separated as if they were on different networks, even when they share the same cables and switches. This is usually done with switch configuration and 802.1Q tagging so traffic stays inside the assigned segment unless routing is explicitly allowed.
In cyber security, VLANs help reduce unwanted access and lateral movement. They are commonly used to isolate guest Wi‑Fi, IoT devices, servers, and management systems so a compromise in one area does not automatically expose everything else. VLANs are especially useful for limiting reach to local device-control protocols, like smart home command channels. However, a VLAN is not a complete security boundary on its own: misconfigurations, weak trunk rules, or VLAN hopping techniques can still create exposure. Good segmentation, access controls, and monitoring are still required.