Adsense, I agree is not by definition affiliate marketing but it is a great way to supplement your income from your website For the beginner, adsense are the little 'ads by Google' that appear on some websites and also on the search engine results pages of Google.
Adsense ads are posted by people who want to generate traffic to a particular site. By allowing these ads to be displayed by Google on your site, there is the potential to make more money
Some adsense ads will result in Google paying you when one of your visitors clicks on the ad [also called pay per click] While others will trigger payment after a thousand impresions [no clicking necessary]
If you have an affiliate marketing site that gets a lot of traffic per day, adding adsense to your site could generate some extra cash
Now the amount you earn per click or impression is very low but with a hich traffic site, the numbers soon add up
Now you have to put your adsense ads in certain areas of your site for maximum effectiveness.
Also, because there are so many ad formats, you need to be able to determine what format is best for you
It is easy to ad asense to your webpages and I can say that it is well worth the effort
More information on adsense at http://www.affiliatemarketingintro.com/Basicguidetogoogleadsense.html