You can limit access to certain categories to the members of specific groups. There are 2 different ways to restrict access to a category:
Method 1:
When editing the configuration of a group, you will see a multi-select field labeled Visible categories. By checking any of the boxes for any category, you will limit access to the category and all products in the category to members of that group:
Method 2:
In the left menu, visit the left-menu item Products > Categories. The system will display a list of all the Categories in the system. Next to each group listed, you will see a link labeled Groups. If you follow the Group link, you will see a pop-up window that displays of all the different groups in the system. By checking any of the boxes for any group, you will limit access to the category and all products in the category to members of certain groups: