User Groups: 

Guest: Not a User Group per se, but included to assist in distinguishing between all users of the web site.

A Guest is anyone that is connected to the web site but NOT registered and/or logged in. A Guest only has access to the Front-end Content that has an Access Classification of Public.

Front-end User Groups

There are four Front-end User Groups available in a standard Joomla! installation:

Registered: The Registered User Group comprises those users who have completed the registration process.

As a Registered User they have the access permission to log in to the web site, view all Content that is Classified as Registered Access as well as Public Access Content.

By default Registered Users are able to configure their own User Profile, submit a Web Link, view/rate Content Items with a Registered Classification,

Author: The Author User Group inherits the access permissions of the Registered User Group and in addition, its members are allowed to create a new Content Item for the Front-end of the web site.

Editor: The Editor User Group inherits the access permissions of the Author User Group and, in addition, its members are allowed to edit all published Content Items for the Front-end of the web site, and to review and edit (where appropriate) any new Content Item that has yet to be published.

Publisher: The Publisher User Group inherits the access permissions of the Editor User Group, and in addition, its members are allowed to publish new Content Items to the Front-end of the web site. In addition the Publisher can control existing published Content Items and Unpublish them if necessary by direct entry into the Content Item itself.