FeedBurner and similar links often include Google Analytics tracking tokens in the URL's query string. These start with the prefix "utm_" (Urchin Tracking Monitor). Facebook and Google also add click tracking identifiers to outbound URLs ("fblid" and "gclid"). They are used by the target site to report back statistics regarding the origin of the inbound link.
This extension removes these tokens from the URL before the destination site is visited, resulting in a more private browsing experience with a cleaner URL that's more suitable for copying into an email, instant message, etc.