This is the Relative Name (Rn) of a VLAN Reference object, a pointer other UCS configuration objects use to refer to a specific VLAN by ID, the naming component that distinguishes this instance from its sibling VlanRef objects under the same parent in the UCS tree. Admins rarely read the Rn directly, but UCSM uses it to build the full Dn path, so it matters when correlating which parent object a given VlanRef instance belongs to. For instance, if two VlanRef objects sit under the same parent container, their Rn values are what tell UCSM (and any script parsing the Dn) apart which one is which.