Refundable means that all or part of the price can be returned to your original means of payment, such as a credit to the credit card used to purchase the flight, perhaps with a big service charge.

This is different from changeable, which means that all or part of the fare, often with a service charge, can be turned into a credit for a different ticket purchased from the same airline. There can be further restrictions in how the credit must be used.

If the ticket is not purchased directly from the airline, additional rules, fees, and hassles/delays can be added.