Affiliate marketing is a new twist on an old concept – commission-based sales. At its simplest, it is a partnership between a merchant and a salesperson where the merchant rewards the salesperson, or affiliate, based on some measure of performance – usually a sale, but in some cases for leads or website traffic.

The first mainstream affiliate marketing system on the internet was launched by Amazon.com, offering Amazon "associates" the opportunity to receive a commission for each book they sold for the company. Since then, many thousands of companies have created their own affiliate programs, encouraging online publishers and salespeople to earn commissions through their partnerships.

There are many publishing and sales professionals who are successful affiliate marketers, but they are certainly not the only people participating in the industry. There are also many "amateur" affiliates – people who build a website, or create an online newsletter, or in some cases simply email their friends and recommend a product or service. In many instances, it's no different to recommending a particular brand or store – except that if somebody follows the affiliate's advice, they're rewarded for it.

Affiliate marketing may involve a number of different strategies and techniques, from building entire online storefronts offering the affiliate merchant's products, adding some form of advertisement to an existing website, to something as simple as making recommendations in an email and including a special affiliate link that ensures that the merchant credits them for the sale.

The growth of affiliate marketing is constantly increasing, as new merchants discover the value of increasing the size of their sales force by creating partnerships with online publishers. This is especially true of merchants whose products or services may appeal to a particular niche market. How better to become established within that niche than by working with companies and individuals who already know the market because they're part of it?