There are several types of affiliate programs. Most will pay you a flat rate or percentage of the sale you make (pay-per-sale). Another common type is when you're paid per action or lead. For example, if you refer someone who signs up for businesses free trial, the business pays you for the sign-up. Although not seen as often anymore, some will pay you per click (this is seen most in contextual ad programs such as Google Adsense) or per impression (each time the ad is loaded on your website).
Affiliate marketing overlaps with other Internet marketing methods to some degree, because affiliates often use regular advertising methods. Those methods include organic search engine optimization (SEO), paid search engine marketing (PPC – Pay Per Click), e-mail marketing, content marketing, and (in some sense) display advertising. On the other hand, affiliates sometimes use less orthodox techniques, such as publishing reviews of products or services offered by a partner.