Final answer:
Managing permissions in Windows Server 2012 R2 involves creating and modifying access control lists within an object's security descriptor, which defines user and group permissions.
Step-by-step explanation:
When you manage permissions in any of the Windows Server 2012 R2 permission systems, you are actually creating and modifying the access control lists (ACLs) in an object's security descriptor. The ACL is a list of access control entries (ACEs) that define the permissions for users and groups to access the object, which could be a file, folder, or even a printer. Through these permissions, administrators can control which users have the ability to read, write, execute, or delete objects within the file system or a network.