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 also viewed, things like that, are just based on the thing you're looking at right now, and showing you things that are similar to it that you might also be interested in. And, it turns out, what you're doing right now is probably the strongest signal of your interest anyhow.

Another example is from Netflix, as shown in the following image (the following image is a screenshot from Netflix):

They have various features that try to recommend new movies or other movies you haven't seen yet, based on the movies that you liked or watched in the past as well, and they break that down by genre. They have kind of a different spin on things, where they try to identify the genres or the types of movies that they think you're enjoying the most and they then show you more results from those genres. So, that's another example of a recommender system in action.

The whole point of it is to help you discover things you might not know about before, so it's pretty cool. You know, it gives individual movies, or books, or music, or whatever, a chance to be discovered by people who might not have heard about them before. So, you know, not only is it cool technology, it also kind of levels the playing field a little bit, and helps new items get discovered by the masses. So, it plays a very important role in today's society, at least I'd like to think so! There are few ways of doing this, and we'll look at the main ones in this chapter.