Affiliate marketing is like promoting products from a certain company through your website for a commission. To use it in SEO, you just have to provide a quality content that makes the users click on the products and visit regularly on your website. So, the more people visit and click on your site, the greater the commission you will get, plus the more traffic it will generate to the company that you affiliate for.
Affiliate marketing is promoting other people product, if the product sold, you get commission in return.
SEO is a study to get free traffic consistently from Google search and affiliate marketing is about making money selling other people product. Knowledge about affiliate marketing is simpler compare to SEO. Driving visitors to a website compose reference to buy something is likely same as a rocket science.
Affiliate marketing is a way of making money online by promoting the products of another company for a commission on each sale you generate.
Affiliate Marketing is a business and a job. You sell other peoples products. You don't have to stock any products, you don't have to deal with customers. I could go on & on about why I love Affiliate Marketing. But I would have to say, what I like about it is you can work your business from any where in the world there is an internet connection. In other words, you can be on vacation a lot. Two words of caution - 1) You can make a lot of money, but you will not get rich overnight like that 13 year old kid did ;-) 2) Just like any other business or endeavor you must be educated to succeed. I started my education in Affiliate Marketing with Rosalind Gardner's Super Affiliate Handbook. If you are serious you owe it to yourself to look at it.