RSS stands for Really Simple Syndication. It is a format used by people surfing the internet to grab updated information (via a 'feed') from their favorite websites.
RSS Feed Readers:
Instead of using Bookmarks, which requires you to visit the website to view updated information, feeds can be used to stream updated information from many different websites simultaneously straight to your RSS Feed Reader (My Yahoo or Google Reader for instance).
RSS and RSS Feed Readers make it possible for people to keep up to date with their favourite websites in an automated manner that's easier than checking them manually with Bookmarks.
On-Site Feed Subscription:
The most common RSS feed icon you will see on a website is an orange button with white radio waves on it. Other colours, for example blue, are sometimes used. The button looks like this.
Browser Feed Subscription:
You can also find a website’s RSS feed by looking at the top of your web browser, on the right-hand side of the address bar, next to the website URL. This is where you will find the Greensheets RSS feed button.