NIS+ introduces a new type of group to name service administration, which NIS does not have. An NIS+ group is used only as a means to provide NIS+ access rights to several NIS+ principals at one time; it is used only for NIS+ authorization.
An NIS+ group is one of the four authorization classes on which access rights are based. The four classes are:
World. All authenticated users. In other words, any user with valid DES credentials. By definition, an object's owner and members of an object's group are also part of the world class so long as their credentials are valid.
Nobody. Anyone who does not have a valid DES credential. If the credentials of some member of one of the other classes are invalid or missing or corrupted or not found, then that user is placed in the nobody class.
Member users of an object's group usually have special privileges to access that object, such as permission to make certain changes to the object. For example, you could add several junior administrators to the admin group so that they can only modify the passwd and hosts tables, but they would be unable to modify any other tables. By using an admin group, you can distribute administration tasks across many users and not just reserve them for the superuser of the entire hierarchy. The NIS+ admin group must have credentials created for its members, even if you are running the domain in NIS-compatibility mode, because only authenticated users have permission to modify NIS+ tables.
After identifying the type of credentials you need, you should select the access rights that are required in the namespace. To make that task easier, you should first decide how many administrative groups you need. Using separate groups is useful when you want to assign them different rights. Usually, you create groups by domain. Each domain should have only one admin group.