The group Administrators contains the user Administrator, which was defined at installation time. The Administrators group is the equivalent of the super-user account. Members of this account can manage user accounts, groups, directories, files, and printers, and can install additional system software. As you can see, the predefined groups are designed to allocate various aspects of system administration and operation. A third type of group, known as Special group, includes a predefined group named Everyone.
All users are members of the group Everyone by default.
By default, all user files are available to Everyone unless the Administrator specifically alters that access. It is possible to change the resources to which Everyone has access. The recommended way to use groups is to assign individual user accounts to a Global group, and then include the Global group in the Local group. Assign the resources with access levels to the Local group. Therefore, Global groups can be thought of as groups of users, and Local groups can be thought of as groups of resources for Global groups.