As an analogy, the news reader acts like a customizable newspaper. You can pull a variety of content from a growing number of sources into one place, to be read however you choose. Sources like major news media outlets (BBC, Reuters, Washington Post) to non-news content providers (Apples iTunes Music Store, the Government of Canada, USGS World Earthquake updates) to smaller independent voices (BoingBoing, VanEats, Sidesh0w). The only stipulation is that the source must provide a feed; many are.
Updated 11:28: There is now a more linking-friendly URL to the description at http://www.mezzoblue.com/subscribe/about/