PNR stands for: Passenger Name Record. It is commonly used in the travel industry and it’s basically a ‘file’ in the database of the system (GDS or CRS/ PMS) which contains information about a passenger (or a group of passengers traveling together) and his travel plans (flight itinerary, hotel booking segments, car rental bookings, etc.).
This concept was first introduced by airlines that needed to exchange reservation information in case passengers booked flights of multiple airlines to reach their destination.
As soon as a passenger books an itinerary, the travel agent or OTA will create a PNR in the CRS it uses. This is typically one of the GDS but if the booking is made directly on a hotel website the PNR can also be in the database of the hotel’ CRS.
PNR reveals all kind of personal data like company, activities, tastes & preferences, credit card details, phone numbers, email addresses & IP addresses. All that allows them to be easily merged with financial and communications metadata.
PNRs are commercial records however they are also used by governments (i.e. to decide whether a passenger is allowed to fly).