Affiliate marketing is a type of performance-based marketing. In affiliate marketing system, a business rewards affiliates, when the affiliates bring visitor or customer. The industry has four core players: the merchant, the network, the publisher (affiliate), and the customer.
Affiliates usually use regular advertising methods. These methods include SEO (search engine optimization), e-mail marketing, google adwords, PPC (pay per click),...etc. WorkFromNoHome is a good guide for affiliate marketing.