PNR is the abbreviation of a unique six-digit alphanumerical code- Passenger Name Record;
The identifier is given to each booking from the airline's system, so the airline can rapidly and effortlessly access your flight and passenger information.
If you have multiple airlines on your itinerary, each airline may have given you its own PNR code assigned to your booking. This is useful to know when contacting your carriers as they each need the correct corresponding booking number to access your information. You can find your PNR codes on your e-ticket as shown below: