It scans your WordPress database and shows what various things old plugins (which were deactivated or uninstalled) left in it. Cleanup is available.
Plugins Garbage Collector scans your WordPress database and shows the tables beyond of core WordPress installation. Some WordPress plugins create and use its own database tables. Those tables are left in your database after plugin deactivation and deletion often. If your blog is more than 1 day old you have some plugins garbage in your WordPress database probably. With the help of this plugin you can check your database and discover if it is clean or not. Extra columns added to the core WordPress tables could be shown also. To read more about 'Plugins Garbage Collector' visit this link at shinephp.com