By default, all of your page impressions and clicks are dropped into one giant bucket. By default, you have no way of knowing how much each individual site earned (if you have multiple sites), or how much each individual page earned, etc. "Channels" are Google's way of letting you break down your earnings into "sections" so you can analyze each website or each page independently to see where the money is coming from. Google only lets you have 200 channels, which is pretty lousy if you have a lot of sites or a very large site. I'll discuss how to get around that in a later section.

Ad Links (or Ad Units)

Ad links, or Ad Units, are just another type of AdSense ad. The basic AdSense ad is blocked of links with short descriptions that when a visitor clicks, you get paid. Ad Links are a little different. They show linked topic that are related to your page, and when people click on those they are then taken to a different page and presented with a list of ads. If they decide to click on one of those ads, you get paid. You can see what Ad Links look like by visiting Google's "Ad Formats" page. It shows all of the available ad format including Ad Links:

https://www.google.com/adsense/adformats


Ad Filter

sometimes Google might decide to show ads on your page that aren't really related to your page content at all. When that happens, You have the option of going into your AdSense account and adding those sites to your Ad Filter. Google will not show ads from any site that you put in your Ad Filter. Also, if your competitor's ads show up on your pages, that's another reason to use your Ad Filter.