Windows Server 2012 R2 Editions (Objective 1.1)

A basic overview of the different editions of Windows Server 2012 R2.
Microsoft Server 2012 R2 Datacenter Edition is aimed at large enterprises as it contains all the features of the Standard edition and allows you to license an (almost) unlimited number of virtual machine instances on the host. It is not available to buy as a retail license.
Microsoft Server 2012 R2 Standard Edition conatains all the features of its Datacenter counter part however it is limited to an additional 2 virtual machines instances within it’s license.

Microsoft Server 2012 R2 Essentials Edition contains all the features of it’s Standard edition counterpart with the exception of Hyper-V, Server Core installation option and Active Directory Federatio Services. It is limited to 1 physical or virtual instance and to 25 users.
Microsoft Server 2012 R2 Foundation Edition is a very scaled down version of the operating system, it is usually pre-installed on physical server hardware and is no support for running it as a virtual instance. It is also limited to 15 users.
 
Microsoft Server 2012 R2 Installation Requirements:

1.4 GHz 64-bit CPU
512 MB RAM
32 GB disk space
 
Microsoft Server 2012 R2 Standard and Datacenter Resource Limits:
64 physical CPU sockets
4TB RAM
64 cluster nodes