Well, like I said Amazon is a great example, and one I'm very familiar with. So, if you go to their recommendations section, as shown in the following image, you can see that it will recommend things that you might be interested in purchasing based on your past behavior on the site.
The recommender system might include things that you've rated, or things that you bought, and other data as well. I can't go into the details because they'll hunt me down, and you know, do bad things to me. But, it's pretty cool. You can also think of the people who bought this also bought feature on Amazon as a form of recommender system.
The difference is that the recommendations you're seeing on your Amazon recommendations page are based on all of your past behavior, whereas people who bought this also bought or people who viewed this...
