[ocdtrekkie]

Basically, this is about ensuring all of the different Windows, .NET, etc. APIs that Microsoft announces work and are available on any of the different flavors of Windows app development you can do. The main thing is that a large category of APIs are available to UWP apps (think Windows 8/10 Modern apps) that aren't available to desktop apps, and Microsoft has been trying to close that gap, since developers have basically said no to rebuilding their apps from scratch for Microsoft's newer app platforms.

The original goal was to force people to move to UWP, which is mobile friendly, processor architecture independent, etc. But the shift was too hard so nobody did it. If all of the APIs are available everywhere, legacy Win32 apps can continue to evolve, and at the same time, Win32 and UWP apps coming closer together makes an eventual shift over to UWP more practical because it won't require starting from scratch.