The Windows 10X is a new version of Windows 10 designed for dual-screen devices like Microsoft's upcoming Surface Neo, which will be available starting in 2020. The “new” operating system will feature a custom UI for these devices.
Windows 10X is Windows
At the Surface event, Microsoft said that Windows 10X will “support Windows apps,” meaning that all traditional Windows graphics apps will work just like they do on Windows 10 Home or Professional. It's not a completely new operating system system, but a customized version of Windows 10 with a UI designed for foldable devices.
Microsoft told The Verge that Windows 10X will run traditional Windows desktop applications in a container to improve battery life. Windows 10X seems to be based on Windows Core OS.
Optimized for dual-screen devices
Windows 10X has a UI "designed and optimized for dual-screen devices, such as the Surface Neo," according to Microsoft.
Surface Neo is a dual-screen device that opens like a laptop computer. Alternatively, they are like two tablets connected together by a hinge.
There will be no Live Tiles
Part of the OS optimization for dual-screen devices appears to be the removal of Live Tiles. There is a new one Start menus with simple icons.
Dual-Screen Tweaks
When you start an application, it will start on one side of the device. It's a bit like the Windows 10 Snap feature - apps will open on one screen (or on one side of the device) and not on both screens. You can drag the application window in the middle of the screen to display it on both screens. Microsoft says that this will not only enlarge the application window on both screens, but will also "optimize" the application interface so that the application can intelligently exploit both screens.
Windowws 10X and dual-screen devices are not currently available. Microsoft will release Windows 10X before the release of the Surface Neo, so developers will have time to try it out and optimize their applications for the new OS.
Microsoft posted on blog one article for the upcoming Windows 10X, but didn't mention many technical details.