This type of marketing generally involves the use of numerous third party sites in helping you sell or market your own site and its products or services. In many cases the relationship is symbiotic, and much like a link change, with the affiliate site asking for a reciprocal link in exchange for posting your own link and products on their site. Others require no link and simply benefit from the traffic your content provides, selling advertising spots. Others make money by selling advertising to you, its vendor for better traffic. And still others ask for a straight commission on sales of your product. When a visitor chooses to buy your product on the affiliates website, they are taken to your shopping cart link, but pass a query string or cookie that makes sure the affiliate gets credit for the sale. When the sales i made, the affiliate gets a percentage of the sale. This is ussualy pretty high, and ranges from 30% traditionally to 50% or more. This is the price paid for someone selling your product for free.
One of the immediate advantages to selling or marketing your site on affiliate sites is the fact its free, in most cases. In theory, it also expands your reach online to many new customers, simply due to the fact you have posted your links or products on someone else's site. If the site is high volume, it can really expand your reach and in theory increase sales. It also, in theory should enhance your search engine rankings, as so many sites are now exchanging link juice back to your site. All these have spawned a large volume of affiliate sites who specialize in selling or marketing vendor products and sites, since there appears so much to gain by both vendor and affiliate alike. Affiliates, in many cases are drawn to the concept that if they get enough vendors in their sites, that enough original content will increase traffic and search rankings, and this increase customers and purchases. Vendors see more affiliates as a way of expanding their own sales using this new network of "partners" online.