What is the difference between a
USER CAL and DEVICE CAL?

A Device CAL is a license to access a device connected to a server, regardless of the number of users of the device. Device CALs are ideal for customers with multiple users for one device, such as shift workers.

A User CAL is a license for every named user to access a server (from any device) regardless of the number of devices they use. User CALs are ideal for companies with employees who need to have roaming access to the corporate network using multiple devices, as well as from unknown devices.