Advanced Permissions introduces more powerful, granular tools for managing your site's content. It replaces the "standard" permissions model that is enabled by default when you install concrete5.
Enabling Advanced Permissions is a permanent modification to how your site funcitons. If you're not sure that you need the features it provides, we recommended creating a full database backup and putting it aside for safe-keeping before proceeding.
Once enabled, you will no longer be able to manage overall permissions on new pages using the Site Access page. Instead, permissions are managed by inheritance from the page above, via Page Type Defaults or manually, using settings that are configured on individual pages. A greatly-expanded list of editing actions will now appear when you put a page in edit mode, mouse over the edit button and click "Permissions."