Answer:
affiliate marketing
Explanation:
Offering a share of the profit of any product to people who do the distribution or promotion for you is affiliate marketing.
It's not just for ebooks. Amazon uses affiliate marketing for all the products they offer on their platforms, sold by them or by other sellers through their marketplace.
It's a good way to attract new customers with a lower cost of acquisition compared to other forms of marketing, like publicity (in any forms).
