RSS stands for "Really Simple Syndication" and is a type XML created to allow lists of information, known as "feeds", to be published by content producers and subscribed to by readers. RSS is used extensively to syndicate Web content such as blogs, news headlines and articles from sources like kbb.com.
These feeds usually contain headlines and summaries, and allow you to link back to the full content if you decide you want more information. Many modern browsers have built-in RSS readers, so often, no other software is needed. To see if your browser supports RSS, look for this icon in your toolbar: