Who has ever used Joomla knows that there are 3 different access levels to manage users' profiling and so to decide how the site's elements (articles, modules, menu items, ...) will be shown or hidden to the users.

These are the 3 access levels: Public, Registered, Special.

But from the Joomla version 3 has been added a new access level, called Guest; let's see all the levels in details.

Public

Every content (module, menu item, ...) with this access level is accessible to anyone, from the only frontend, regardless the user is signed in or not.

Guest

Every content (module, menu item, ...) with this access level is accessible to anyone if the user is not signed in, but it becomes inaccessible if the user signs in the frontend. This is a useful and interesting level which can be used, for example, for a login module which must be displayed to the users not signed in but it must be hidden when the users sign in; set the Guest access level to the module solve the problem.

Registered

Every content (module, menu item, ...) with this access level is accessible only to the registered users (of every levels) which are signed in the frontend. Let's remember that the Registered level users can sign in only in the frontend and they can't add articles to the system.

Special

Every content (module, menu item, ...) with this access level is accessible only to the user with the Author permission (or above); obviously the user must be logged