Pinpoint Salintiy Meter scale

Sorry if this has been covered before but, the Pinpoint Salinity meter measures in Ms. I did a terrible job of explaining to a fellow refer just exactly that was as we were comparing tank parameters. I think it is a measure of conductivity and not actual salinity? Is Ms micro Siemens? Next time a reefer says they run their tank at 32.8 (ppt) and tell them I run mine at 50 (Ms) I would like to do a better job explaining what that is lol