This reports the current membership status of this interface in the VSAN - for instance whether it's actively a confirmed member, pending, or in an error state. An FC port can be configured to join a VSAN's trunk but fail to actually establish confirmed membership, for example due to an ISL trunking mismatch with the neighboring switch, so this status field is what an admin checks to confirm the membership actually took hold rather than just being requested. A member status of error on an FC trunk port would explain why that port isn't seeing the rest of the VSAN's fabric even though it's configured to be a member.