The technology behind RSS allows internet users to subscribe to websites that have provided RSS feeds; these are sites that change or add content regularly. To use this technology, users are required to download an aggregation service, which presents new articles in a list, giving a line or two of each article and a link to the full article or post. RSS subscriptions are free. It is an easy way to be alerted when new content appears on your favorite websites. See all your favorites in one place.
Information is delivered as an xml file called an RSS feed. RSS allows a website's frequent readers to track updates on the site using a news aggregator. The aggregator or reader allows content to be brought together and displayed via a web browser, email, or as a stand alone application.
You will find more detailed information about RSS when you choose your reader.
Refer. (Wikipedia)