Launching as part of Windows Server 2008, the platform was a decade late compared to arch-rival VMware which launched in 1998. It is has been a part of every Windows Server edition since and is also available as a free version which is standalone without the full server software component. The free version is not just a demo; it offers a fully featured bare metal hypervisor and has been used successfully in cloud type application that requires the clustering of resources and connection from clients.
Who is it aimed at?
If you ask Microsoft, Hyper-V is for absolutely everybody across every use case. However, although performance is comparable, VMware vSphere has an advantage in terms of high end features and management elements. In addition, VMware has slightly better support for Linux versions and slightly more support from third party software developers that specifically target virtualised environments.
There used to be a notion that Microsoft was better for small environments while VMware owned the larger enterprise space. This distinction is less clear with every version of both platforms. Microsoft has committed a lot of development resource into Hyper-V and its entire virtualisation effort and is catching up fast.