An RSS feed is a listing of a Web site's content to which you subscribe using an RSS reader.  It is updated whenever new content is published to the site. To subscribe to a feed, click on the RSS icon.  The icon typically looks like this:

This will take you to a new page. Copy and paste the address of the new page (e.g."http://supportingcast.mannlib.cornell.edu/newbooks/rss.php?class=QC&loc=phys") into your news reader of choice.