When you sell a copy of Windows Server, the customer will receive a server license permitting installation of the operating system on one computer. A server license by itself does not provide the legal right for others to connect to that computer, whether they work for the company or not. Instead, each user needs a Client Access License (CAL).
Customers will need a CAL for each employee, or each employee device, that accesses the Windows Server installation, but not for anonymous users who access it over the Internet.
Server CALs are cost effective and affordable, allowing customers to pay only for the licensing they need with the option of buying more as their businesses grow.
For Named User to access a server
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.
Free Access from anywhere, any device
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.
