Source: http://www.ipowerweb.com/editorial-library/EDL-glossary.html

RSS (Really Simple Syndication)
RSS is a format for sharing content among different websites. Sites can syndicate “feeds” (content) and Internet users can use an application called an RSS reader or aggregator to download feeds. There are many such readers available, most at no cost. To explain the difference between RSS and email, think of email is a push technology. You have to wait until the email is sent before receiving it. On the other hand, RSS is pull technology. The RSS reader constantly scans each of the feeds to which you have subscribed looking for new information. Once found, the reader notifies you and captures that information for viewing inside the application.