For a lot of website owners, Adsense and Amazon are two primary ways to make money. Adsense is a PPC ad network, whereas Amazon provides Affiliate Ads. You earn from Adsense when a visitor clicks on Adsense ads, whereas you will earn from Amazon ads when a visitor clicks your Amazon ads and buys the product. I have not earned much with Amazon Ads but I earn from Adsense from my 6 blogs.