RSS stands for Really Simple Syndication and represents the standardized web feed syndication. That's quite a mouthful. What does it mean?
Think of it like the New York Times crossword puzzle. The New York Times is the home of the puzzle, but it is also printed in newspapers across the country. This is called syndication. To facilitate this on the web, a standard is needed to pass information back and forth. That's where RSS comes in. It provides the standard for syndicating articles on the Internet.
Most of us run across this syndication every time we browse the web. A site that is syndicated will usually advertise its RSS feed using the orange icon pictured above this article. Some sites will also use icons for common RSS feed aggregators like Yahoo, Google or Netvibes.