Windows Server 2012 R2 Client Access Licenses (CALs) are required to regulate and manage access to the services and resources of a Windows Server 2012 R2. CALs ensure that only authorized users or devices can access the server, which helps organizations meet licensing requirements and control server access. The two main types of CALs offer flexibility and are tailored to different usage scenarios:

User CAL: This license allows a single user to access the server from any number of devices, making it ideal for mobile or remote employees who use multiple devices.

Device CAL: This license allows a specific device to access the server, regardless of how many people use that device. This option is ideal for workstations with shared devices, such as in shift operations or communal workstations.

Windows Server 2012 R2 CALs help organizations securely and efficiently manage access to centralized resources, make the best use of server resources, and easily scale their IT infrastructure. Choosing between User and Device CALs allows organizations to flexibly adapt the license type to their working structures and thus ensure legally compliant use of the server.