What is RSS?
RSS stands for Really Simple Syndication and is a form of XML (eXtensible Markup Language). RSS is a standard data format to distribute news content, though it can be used to share almost any type of information. The format was originally developed by Netscape for sharing information across portals, but when Netscape lost interest the format was developed further by Userland for their weblogging software and services.
RSS really took off when thousands of bloggers started to use it to publish their own content and read content from other weblogs. Commonly termed as syndication, most major news sites such as BBC, Google News and CNN use this method to share their content to other RSS-aware sources. These sources may be third party websites, desktop applications or software - pretty much anything that can read and parse data.
The logo shown is often used to represent a link to an RSS feed on a website.
More information is available on Wikipedia.