A flight number (e.g., DL422) is like a "bus route" name; it identifies a specific flight operated by an airline on a specific route and schedule (e.g., Delta's daily flight from Atlanta to London). Multiple people are on this flight, and the number stays the same every day. A flight confirmation number (also called a Record Locator or PNR) is a unique 6-character alphanumeric code (e.g., XJ9L2P) that is specific only to you and your reservation. It is the "key" used to check in, manage your seat, or change your booking. Think of the flight number as the "address" of the plane in the sky, while the confirmation number is your "digital ticket" that proves you have a reserved seat on that specific plane.