There's another thread above yours regarding the very same issue. Check it out.
Several of us newbies have been given these numbers.....we're on our first cruises and not sure what they mean.
I spoke to Princess tonight. I suggest you call 1-800-PRINCESS and ask them directly.
My understanding is that all NEW cruisers got this number for FUTURE bookings...to start a "profile" or a "record." By cruise #2 you are "gold."
We're getting nothing special now.....but we should use our Circle number when we book in the future to be assured of "specials," etc. It would establish our "history" as previous cruisers with Princess.