The goal is to promote products, or affiliate links, that are made by other people and earn a commission when you make sale. This is very popular because anybody can enter in this business with no experience. There are tons of online resources that teach you how to do it.
You could promote the affiliate links on your website, blog, inside your eBook, forum, via e-mail, etc.
This way you don’t have to invest time, effort and money in coming up with a product. Somebody else has done that already, you only have to promote it and earn commission every time somebody buys the product through your links.
The most popular Affiliate program is: