What does denied boarding compensation refer to?

Denied boarding compensation specifically refers to compensation provided to passengers who have been involuntarily removed from a flight, often due to overbooking. Airlines frequently sell more tickets than available seats on a flight, leading to situations where some passengers may not be allowed to board despite having reservations. When this happens, the airline is typically required to compensate those passengers, which can include monetary payments, vouchers for future travel, or services such as meals or hotel accommodations, depending on the circumstances and regulations.

This practice protects consumers and ensures that they are not left without recourse when they are unable to fly as planned due to the airline's decision to overbook. The other options relate to different issues: refunds for delayed flights, assistance for lost luggage, and reimbursement for canceled tickets do not involve the specific circumstances of denied boarding. Thus, the correct answer focuses on the essential nature of denied boarding compensation.