What is Affiliate marketing?

Internet Affiliate Marketing Is one of the few Internet Marketing ways to earn.
Affiliate marketing is a web-based marketing practice in which a business rewards one or more affiliates for each visitor or customer brought about by the affiliate's marketing efforts.
Affiliate marketing involves in promoting other online company's product.Each Product that is promoted and sold will earn you up to 75% per sales depending on what product you are promoting.

Affiliate marketing also overlaps with other internet marketing methods to some degree, because affiliates often use regular advertising methods. Those methods include organic search engine optimization, paid search engine marketing, email marketing and in some sense display advertising.

So by promoting other people product=>A person purchase the product=>Earn$$

I'm lost any help?