Windows Server 2019 Essentials Ed ROK (25 Users)

Windows Server Standard

 Windows Standard is designed for small or medium-sized businesses that need more than 25 users or multiple servers to separate different server roles. In fact, by using only the Standard edition of Windows server, you can separate Flexible server manager operations (FSMO) roles across multiple servers and ensure higher security of your environment.

Windows Server Datacenter

Server Datacenter is typically used for virtualization where a large number of virtual machines (VMs) are hosted on a single physical host. It requires CALs in the same way as the Standard version, but allows an unlimited number of virtual machines to be run.

However, the cost of a Datacenter license is about 7 times the cost of a Standard license, so if you are running fewer than 14 VMs on a physical server, it will generally cost less to get only Standard.

Note that when you purchase the Essentials edition, you will not need to purchase any Client Access License (CAL) as you do for Standard and Data Center.

Microsoft is not actually planning to release the next version of Essentials. Windows Server 2019 Essentials is likely to be the last version of Windows Server Essentials

Microsoft recommends small businesses to move to Microsoft's cloud products (Microsoft 365, Office 365)