Think of an RSS feed as a well-trained dog fetching your morning newspaper.

Whenever you see this orange icon:  that means there is an RSS feed available. I’d Rather Be Writing offers this simple and useful definition:

RSS stands for really simple syndication. It’s a way to automatically pull the latest posts from blogs into a news reader, such as Google Reader (my favorite) or Bloglines. That way you don’t have to visit each site individually to see what’s new.

Below is an easy-to-understand, amusingly low-tech video by Commoncraft, which explains the difference between the "old" way of reading web content (going out to each site every day to see if anything is new) and the "new" way (having new content delivered to you via RSS):

I love the creativity of these guys! With nothing more than paper drawings and an erasable marker, they explain exactly what makes an RSS so useful:

The Old-Fashioned Hard way to read the Web: 
Each day you visit all your websites and blogs to see if there’s any new content.

The New Easy Way:
RSS brings all your website content to you as soon as it’s available!