If you have banned users there is no reason for them to visit your site at all. So with this mod it will redirect them off site. You can send them to a friendly site such as google or you can send them to a nasty site. You can even send them to your competitors or rivals site, let them deal with the banned users.
The Lite version uses usergroup 8 as the banned usergroup, the Pro version you can choose which usergroups are the banned ones. In the Lite version banned users will be redirected to google.com.
There is another cool feature with this mod, lets say you don't want to ban a particular user, but you want to make his browsing experience less than desirable. With this mod you can torment these users by slowing down page rendering times on your site for them. Say setting it to 20 (seconds) each time they changes pages it will take a additional 20 seconds for the pages to load in their browser.