There are two editions of Admin Tools: Admin Tools Core and Admin Tools Professional. They are targeting different user groups, based on their security needs and experience level.
Admin Tools Core is the Free (as in “free speech” and as in “free beer”) edition which contains the necessary features to update your core Joomla! installation, fix directory permissions and perform database maintenance. It’s what we believe that all sites shouldn’t do without, in one neat extensions. However, it is missing all the active security enhancing features of the Professional release. It’s recommended for administrators of very small sites.
Admin Tools Professional, on the other hand, is the for-a-fee edition which has those extra features only useful to larger sites which require active security. We recommend it for power users and web professionals who want to enhance the security of their web sites.