Specifies the string that identifies a collection of system users that can access and work with protected resources. The system uses groups to control access to files and resources by users who do not own them. When a user invokes a process, the system associates the process with the user's ID and the group IDs of the groups of which the user is a member. If the user owns the resource or is a member of a group that can access it, the system grants read, write, or execute access to it according to the access control list of the resource or file.