A refund is you returning the money by your own decision, within the refund policy. It's different from a chargeback, in which the buyer goes to the bank and the amount is taken back by force.
The difference matters more than it seems. The refund returns the amount and closes the matter. The chargeback returns the amount, charges a fee, eats into your dispute quota, and, if it piles up, takes your account offline.
That's why refunding quickly when the buyer asks is a financial decision, not a courtesy: it costs less than the same return arriving through the bank's route.