These are very special affiliate programs where the merchant commits to pay you for a longer duration. Say, you have generated a lead, which has been buying products or services in several occasions; the merchant also pays you for each sale. So, it becomes a lifetime earning for you for every sale made by the merchant to the customer/
consumer, you refer. You recommend just once and then money comes to you automatically for his every purchase. You hardly need any further effort or time to facilitate this lifetime earning. The merchant pays you a percentage of the money paid by the referrals for purchasing their goods or services. Your bank account gets flattened because the commission accumulates.
You might compare them with Amway or Pioneer eBizz.