Ever seen an icon, similar to the following screenshot, on the web, before?
These icons are indicators that the site's owner wants to share his content with you. If you ever subscribe to a podcast, or read a blog in a newsreader, then you've used an RSS feed. RSS is a standard way of sharing your Drupal web site without visitors needing to come back to your site each day (or hour, or minute) to check if you have new content.
Note
RSS stands for Really Simple Syndication or Rich Site Summary, depending on who you ask. It was created by Ramanathan V. Guha, Dan Libby, and Dave Winer in the late 1990s, and has become a standard for sites that have frequently updated content.
Users subscribe to your RSS feed in their own newsreader. Periodically, the newsreader automatically checks the RSS feed to see if there is any new content there. If there is new content, the newsreader downloads a summary of the article and alerts the user that there is new content. If that person is interested...