The document discusses Joomla access control lists (ACL). It begins with defining ACL as access control lists and discussing how they control the visibility of content and actions on objects. It then provides an overview of how ACL permissions are set at the global, component, category, and individual object levels, including how permissions are inherited between levels. It discusses how the ACL Manager extension for Joomla simplifies complex permission settings for user groups based on categories. Resources for further information on Joomla ACL and developing extensions with ACL support are also listed.