http://news.google.com/intl/en_us/news_feed_terms.html
Available Google News Feeds
Google News section feeds: You can get a feed for any Google News section. For instance, if you select a feed link while you're on the Business page, you'll get a feed of business news.

+ sehr gute Erklärung, auch technische Erklärung
http://de.wikipedia.org/wiki/RSS

+ gute Erklärung (dt) worum es geht
http://twoday.tuwien.ac.at/hilfe/stories/56

+ if you go to http://www.marketingstudies.net and click to the red question mark (right of the red RSS-Button) this leads to an explanation from the view of using RSS for marketing purposes and to further leading links.
+ very good explanation also in the BBC Homepage
http://news.bbc.co.uk/sport1/hi/help/rss/3397215.stm
from the view of a news provider. Also information: How do I start using RSS feeds?.