Autodiscovery makes it possible for browsers and other software to automatically find a site's RSS feed.  When a browser loads a page and discovers a feed is available, Firefox and Internet Explorer display the common feed icon in the address bar.

Internet Explorer 7:

Mozilla Firefox:

Users can click the feed icon to subscribe using the browser's RSS reader or another preferred reader. Autodiscovery helps your feed(s) reaches a wider audience. 

To setup autodiscovery web publishers simply need to add the following code inside the header of your main page and any additonal pages where a user might want to know that a feed's available. You can include more than one autodiscovery link but each must identify a different feed.  The main feed should be listed first.