What is Hyper-V?
Microsoft created Hyper-V as a virtualization tool in 2008 and due to its success it has continue to released new versions in tandem with windows server versions. Currently, there are a total of four different versions which are Windows Server 2008, 2008 R2, Windows Server 2012 and 2012 R2 respectively.
Since inception, Hyper-V has always been a Windows Server feature, however it is also available as a stand alone product which is one of the major reasons which lead to its widespread popularity.
Hyper-V acts as a stand alone pulped down version of Windows Server. In short, Microsoft trimmed down all the unrelated Windows Server functions, keeping only exactly what you need to run this powerful virtualization platform in the most efficient method possible.
Licensing in Hyper-V
This product is entirely stand alone and does not require any operating system license. You will however need to buy licenses for any instance of Windows which would operate on each individual VM. In perspective, this gives you the freedom to set up Hypervisor in any way which you see fit and thus providing the best result for your company.