Take this link, for example: http://www.amazon.com/TTL-Cookbook-Donald-Lancaster/dp/0672210355?ie=UTF8&tag=ft0fc-20&link_code=btl&camp=213689&creative=392969
The affiliate link is this: tag=ft0fc-20
You can then tack &tag=ft0fc-20 onto any Amazon link, spam it on a forum, and whomever the tag belongs to (In this case, a high school math teacher I know in NY, because I live in CA and lost access to the affiliate program) gets a 4-10% cut of not just that product, but ANYTHING ELSE you happen to buy after clicking it.