Native VLANs are VLANs that can pass through trunk ports without needing a VLAN tag. A trunk port is a port that can carry traffic from multiple VLANs, which are logical groups of devices that share the same broadcast domain. A VLAN tag is a piece of information that identifies which VLAN a frame belongs to. A native VLAN is usually used for backward compatibility with devices that do not support VLANs, or for untagged traffic that does not belong to any VLAN. By default, the native VLAN is VLAN 1, but it can be changed to any other VLAN.