Recurring commissions are affiliate commissions based on recurring billing products sales. Affiliate earn commissions for the initial sale, but earn also commissions for each new billing.
More common recurring billing products in affiliate program are :
web hosting services
membership sites (dating, adult, etc.)
products with trial periods
Recurring commissions are sought by potential affiliates.
However, reccuring commissions generally can’t be tracked directly by an affiliation platform and that can be an issue for affiliate payments.
See also lifetime commission as it is another kind of affiliate commission.