Channels enable you to view detailed reporting about the performance of specific pages and ad units. By assigning a channel to a combination of sites, or pages or ad units, you could track the performance of a leaderboard versus a banner, or compare your motorcycle pages to your automobile pages. You can even create a channel to track each of your separate domains, so you can see where your clicks are coming from. While channels can be used to track performance and revenue, they won't have any effect on your earnings or ad targeting.
There are two types of channels from which to choose: URL channels, and custom channels
For printnpost authors, the only need for channels is if you have more then one author account or use adsense on another website.