PNR? What's that

In checking a flight booking I've got, I noticed a number on my ticket - a PNR number. Very odd, and also very Orwell's 1984 esque - this site explains how the tracking of your activities works:

"If you are a regular customer or have a corporate or frequent flyer account with an airline or travel agency, your account information is typically stored in a "profile" in the CRS/GDS that is automatically associated with, and often copied into, each PNR created for you. That profile might include all the credit cards you regularly use (even if you aren't using them for this purchase); alternate addresses, phone numbers, and emergency contacts; names and other information on your family members or business associates who sometimes travel with you (even if they aren't on this trip); notes about your tastes and preferences ("prefers king bed", "prefers room on low floor in hotels", "always request halal meal", "won't fly on the Jewish sabbath", "uses wheelchair, can control bowels and bladder"; "prefers not to fly Delta Airlines"); personal notes intended for the internal use of the travel agency ("difficult customer -- always changing his mind"); department and project billing and approval codes for corporate travel; all your frequent flyer numbers (even ones you aren't using on this trip) and a wide variety of other information."

PNR Explanation