RSS (Rich Site Summary) is a format for delivering regularly changing web content. Many news-related sites, weblogs and other online publishers syndicate their content as an RSS Feed to whoever wants it.
RSS solves a problem for people who regularly use the web. It allows you to easily stay informed by retrieving the latest content from the sites you are interested in. You save time by not needing to visit each site individually. You ensure your privacy, by not needing to join each site’s email newsletter.
Feed Reader or News Aggregator software allow you to grab the RSS feeds from various sites and display them for you to read and use. A popular aggregator is Google Reader. It’s easy to use, and, like all good web applications, it’s free.
You can find out even more about RSS here.