This is the actual, currently-resolved name of the VM network definition this reference points to, as opposed to the admin-configured target name. When this differs from the configured vmNetworkDefName field on the same row, it's a direct sign that this specific reference is currently pointing at a fallback or stale definition rather than the one an admin intended, which would explain unexpected VLAN behavior for VMs using this network set. If vmNetworkDefName says 'vlan210-def' but operVmNetworkDefName shows something else, that mismatch alone tells you this reference isn't resolving as configured, likely because the intended definition doesn't currently exist.