Windows Server 2012 Editions
Here’s an explanation of the four Windows Server 2012 editions.
Windows Server 2012 Datacenter and Windows Server 2012 Standard
There is no major difference between the two. They are both fully-functional editions of Windows Server 2012. They both support the same number of processors and memory. They also offer the exact same features and functionality. For example, both support high availability features like failover clustering. The only difference between the two is the support for the number of virtual machines.
Window Server 2012 Standard edition allows you to run up to 2 virtual machines on up to 2 processors. Windows Server 2012 Datacenter edition is meant for virtualization and private cloud deployments and you can have unlimited number of virtual machines on up to 2 processors.
For more information you can check out this Windows Server 2012 Licensing and Pricing FAQ.
Windows Server 2012 Essentials
The Windows Server 2012 Essentials is the next version of Windows Small Business Server (SBS). In this version, some of the features are stripped down while others are added to support a small business environment.
For more information, including datasheet, FAQs, and benefits of Windows Server 2012 Essentials, click here.
Windows Server 2012 Foundation
Windows Server 2012 Foundation is a special edition that is only available through OEMs. This edition has no virtualization rights and is limited to only 15 user accounts.