"Confidential" rates are usually used for Hotwire/Priceline or Expedia rates where the hotel provides a net rate and then the consumer buys it at a marked up price. Neither the hotel nor the website wants consumers to know the actual revenue the hotel is getting.

PMS refers to the "Property Management System" which is what the hotel uses to actually check you in, manage availibility at the hotel etc etc. Hilton is unique in that they have one common PMS for all hotels in the Hilton Family. A PMS rate is usually a rate that is only open locally (e.g. a walk-in rate) and not sold in the GDS or hilton.com etc.

Why a rate would show up as both confidential and a PMS rate is beyond me....but it must be some sort of glitch between the PMS and the Hilton central reservation system.