You can create as much categories as you need for your project.

A category can have a unlimited number of sub-categories if needed

Access rights categories

The access rights settings are extended from the core Joomla possibilities.

Standard, mostly set to public in the configuration of your Joomla! installation, is the standard setting from the configuration.

Groups

In the groups setting you can set the minimum usergroup level which can access the category and the usergroups above that level.

Preset

This setting gives you the ability to set the one usergoup or more groups that can access the category and it's items.

Inheretance

If you add a item to a category, the item gets the same access rights as the category it belongs to.