The difference between user cal and device cal
license your deployments with device or user client access licenses
each user or device accessing a licensed windows server requires a windows server cal or a windows server and a remote desktop services (rds) cal.
remote desktop services user cals
remote desktop services user cals
it allows a user to establish a remote desktop session on a remote desktop session host server. regardless of the number of devices that the user uses to log in.
remote desktop services device cal
remote desktop services device cals
it allows a specific device to establish a remote desktop session on a remote desktop session host server. regardless of the number of users connecting from of this device.