Hi Rafise,
this is from documentation:
VLANs
VLANs (Virtual LANs) are a common way to create logically separate networks using the same physical infrastructure.
Managed switches can assign VLANs to each port in either a “tagged” or an “untagged” manner. A VLAN is said to be “untagged” on a particular port when it is the default VLAN for that port, and requires no special configuration in order to access it.
“Tagged” VLANs can also be used with nodes in MAAS. That is, if a switch port is configured such that “tagged” VLAN frames can be sent and received by a MAAS node, that MAAS node can be configured to automatically bring up VLAN interfaces, so that the deployed node can make use of them.
A “Default VLAN” is created for every fabric, to which every new VLAN-aware object in the fabric will be associated with by default (unless specified otherwise).