Amazon associates, how do you make money from there?

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So, how does it actually work? I mean to be an Amazon associates, and earn some extra money? Do you simply sign up, and either pick a link or banner to post on your website, or use widget? I have no idea how it actually work. Can you design a website perfectly similar to Amazon simply for selling, and you just bring up everything from Amazon database, and help them sell their items, and earn the commission? Would this Amazon associates work too? Anyone who has earned money from this program please give me some advice?