Windows Server Editions - How to Choose between Datacenter, Standar, Essentials and Foundation

Windows Server 2012 R2 is available in four editions designed to suit a variety of customers needs.

• Datacenter and Standard are ideal for private cloud. 
• Essentials and Foundations are optimal for small businesses. 

Windows Server 2012 R2 Datacenter
Windows Server 2012 R2 Datacenter will continue to be the ideal edition for highly virtualized private and hybrid cloud environments providing customers with unlimited virtualization rights in all of the enhanced and new features of Windows Server 2012. The licensing for Datacenter will continue to follow a processor + CAL model however now each license will cover up to two physical processors on a server.
Windows Server 2012 R2 Standard
Windows Server 2012 R2 Standard is ideal for physical computing or lightly virtualized environments providing customers with an additional virtual instance than the previous version for total of two virtual instances along with all of the same features as the Datacenter edition but licensing for Standard is now the same as Datacenter with a processor + CAL model with each licensing covering up to two physical processors on a server.

Windows Server 2012 R2 Essentials
Windows Server 2012 R2 Essentials is a cloud connected first server ideal for small businesses with up to 25 users providing customers with the flexibility to have email in the cloud, runtime of business applications, or run email on premises. The licensing for Essentials will continue to be a server model with no CAL requirements.
Windows Server 2012 R2 Foundation
Finally Windows Server 2012 R2 Foundation is an economical general-purpose server for physical computing environments only. It provides customers with a Windows Server experience for up to 15 users the licensing for Foundation will continue to be a server model with no CAL requirement.

Comparisons
Windows Server 2012 core editions Datacenter and Standard are both private cloud optimized solutions providing all the same features and capabilities and cost effective virtualization options. Datacenter is ideal for a highly virtualized environments and provides for unlimited virtualization. This edition is ideally suited for rapidly growing businesses with high density virtualization needs. Standard Edition is optimal for low-density environments or for those without virtualization needs as each license provides for two virtual instances. Both Windows Server 2012 R2 Datacenter and Standard editions are only differentiated by virtualization rights. Datacenter provides for unlimited virtualization and Standard provides customers with two virtual instances with each license . Both editions share a common licensing structure based on a processor + CAL model where each license will cover up to two physical processors on a single server. There is no difference in the available features of these two editions since Standard edition now has all the same features that were previously only available in the Datacenter edition.