Microsoft have changed the number of variant of Windows Server platform. Prior to 2012 Microsoft had more than 6 variants of the Windows Server platform. In Windows Server 2012 they limited it to just 2: Standard and Data center. The rest of the variants has bee merged into these two or as features or roles within these two.
In Windows server 2012 Microsoft implemented advanced features that once were the domain of only large enterprises.
Such features include: thin-provisioning, high availability and storage de duplication. All these and other advanced features are available in the Windows Server 2012 Standard version as well. You should consider the Data center version if you are going to use it on a virtualized environment.
The standard version license allows you to run Windows Server up to two virtual machines on two processors.
Windows Server 2012 has the Windows 8 new user interface and welcome screen. But considering the significant amount of improvements implemented in this new operating systems you should consider this to be your new server operating system for the near future.