I'm going to go deep on individual new features in Windows 10 version 1803 ("Redstone 4") as they're revealed. So let's catch-up and start with something visual: The Fluent Design System.
One of the more interesting and confusing aspects of Windows 10 is that there isn't any one thing called Windows 10. Instead, Microsoft maintains various pre-release and production releases of the system simultaneously. And on top of that, it also updates the built-in apps on their own separate schedules.