Windows Server 2019 Licensing:

Windows Server 2019 Standard and Windows Server 2019 Datacenter alternatively both follow core-based licensing models, where licensing requirements are determined based on the number of server cores instead of the number of processors. The transition from processor based to core based licensing was first introduced with Windows Server 2016 Standard and Datacenter to provide a more consistent licensing experience across multi-cloud environments.

Each server requires a minimum of a single Base License, which covers 16 cores.

All physical cores of the server must be licensed. Keep in mind, Windows Server Additional Licenses may be required in addition to Base Licenses to cover cores on systems with more than 16 cores in total.