A content source is any source of content you would like to use to pull into your Cerkl. Oftentimes, this includes your organization's blog(s) or your other pages with an RSS Feed, as well as any other external content source you feel complements your organization's content.
Providing more sources of content to your subscribers allows them to personalize their interests even more! If you don't approve of some content from another source, you can always disable it.
To add, enable, or disable a content source, go to Content > Sources.