RSS (or Really Simple Syndication) feeds are free content feeds from Web sites,  that contain article headlines, summaries and links back to full-text articles on the web.

To start using RSS, you need a special news reader or aggregator that displays RSS content feeds from Web sites you select. There are many different news readers available.

List of news readers (Yahoo)
List of news readers (Google)

To use your news reader, you simply subscribe to the RSS content feeds you want.