In affiliate marketing, commissions refer to the payment that an affiliate earns for promoting a product or service. The payment structure for affiliate links can vary depending on the affiliate program. Some common payment structures include pay-per-click, pay-per-sale, and pay-per-lead. With pay-per-click, affiliates earn a commission for every click on their affiliate link, regardless of whether a sale is made. With pay-per-sale, affiliates earn a commission only when a sale is made through their affiliate link. With pay-per-lead, affiliates earn a commission when someone completes a specific action, such as filling out a form or signing up for a trial, through their affiliate link. The commission rate and payment structure vary by affiliate program