The booking reference number, also known as a PNR (Passenger Name Record) or "Record Locator," is a unique 6-character alphanumeric code (e.g., QW3ERT) that serves as the digital fingerprint for your entire travel reservation. This code is generated by the airline's computer reservation system the moment you complete your booking and is used to consolidate all your travel details—including passenger names, flight segments, seat assignments, meal preferences, and payment status—into a single master file. It is the most critical piece of information you need for managing your trip; you will use it to check in online, select or change your seats, add checked baggage, and retrieve your digital boarding pass. Unlike a ticket number, which is a 13-digit sequence specific to the financial transaction of the seat, the booking reference identifies the itinerary itself. If you are traveling in a group under one reservation, everyone will usually share the same booking reference. It is essential to keep this code private, as anyone with your last name and this reference number can access your personal travel details and potentially make changes to your flight via the airline's website or mobile app.