Microsoft is providing a free virtual machine that comes preloaded with Windows 10 Enterprise, Visual Studio 2017, and various utilities in order to promote the development of Universal Windows Platform apps. Before you get too excited about a free version of Windows 10 Enterprise, this Virtual Machine will expire on January 15th 2018.
When downloading the development environment, you can choose either a VMware, VirtualBox, Hyper-V, or Parallels virtual machine depending on what virtual machine software you use. Each of these images are about 17-20GB when extracted from the downloaded archive and include almost everything you need to develop Universal Windows Platform apps.
Included on the site where you download the VMs are a wide array of samples, tutorials, and documentation for those who want to learn how to developer apps for Windows 10.
Unless you have a license for VMware, Parallels, or are running Windows 10 Professional, I would suggest that you use VirtualBox and its corresponding virtual machine when playing with the development environment. This is because VirtualBox is free and supports snapshots that allow you to save various states of the VM so that you can restore them later.
When installing via VirtualBox, you will need to import the appliance and when it asks for the OVA file, point it to the file you downloaded and extracted. Just use the default settings above, with additional allocated RAM if you spare it, and then click on the Import button. Once imported, you can start the guest and begin to learn how to develop Universal Windows Platform apps.
Just remember, you only have until January 15th 2018 when the Windows 10 Enterprise license expires.