Microsoft Windows Server 2019 Datacenter

Windows Server Datacenter is mostly used for virtualization as it allows you to place many virtual machines (VMs) on one physical host. Datacenter, same as Standard, requires CALs but allows running an unlimited number of virtual machines.

However, the cost of a Datacenter license is a lot higher than a standard license, so if you are running fewer VMs on a physical server, it will generally be less expensive to purchase just the standard.