Up to now, we've used the user groups and their sets of permissions that are available in Joomla out of the box. However, you can also create custom-made user groups and assign them permissions to do and see just what you allow them. Instead of using the existing user groups and their predefined sets of permissions, you can create as many groups as you want and grant the people in those groups any combination of permissions. If you want, you can set permissions for specific parts of the site—permissions apply to either the whole site, or to specific components, categories, or items (such as a single article).
Creating a custom user group and assigning permissions involves the following four steps:
Create a user group (a group of people sharing the same permissions).
Tell Joomla what the group can see. What's visible on the site, what's hidden from them? In Joomla terms, this means you assign a Viewing Access Level to the group.
Tell Joomla what the group can...