Affiliate Marketing is an online method of making commission by promoting participating web based businesses. You, as an affiliate marketing member, will be rewarded for delivering website traffic in one of the following categories:
A visitor to the company's website.
A subscriber to that company's website / newsletter etc.
A paying or registered customer of the business.
...as a result of your affiliated promotional effort.
Cost per impression, often abbreviated to CPI or CPM,
cost per mille (thousand),
unique visitor (UV),
registrant or new customer (pay per lead),
sale - usually a percentage,
pay per sale or revenue share,
or any combination of the above.
Web based merchants quite like affiliate marketing because it is a proven "pay for performance model", meaning the web based merchant does not incur a marketing expense unless specific marketing strategy results are realized. But also retains control of their persona by placing restrictions upon the affiliate's modus operandi. For example disallowing PPC (Pay Per Click) methods by the affiliate or banning the use of the merchants name or URL as a keyword in any of the affiliates website page names, titles, headings etc. - common restrictions.