With the latest Windows 10 Insider build, new hidden features have been found that add long-awaited media controls to the volume flyout and a new settings page that shows a ‘What’s New’ section for the current Windows release. Microsoft developers work on new features for Windows 10, they hide them from being used by users. These features can be enabled using tools like Mach2 or ViVe, but as they are still in-development, they can cause Windows to not work properly. Microsoft is adding a new setting page that will list all the new features with detailed instructions on how to use them.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-the-new-hidden-features-found-in-preview-builds/