This is Microsoft’s new modern File Explorer for Windows 10X

[Windows Central]

Microsoft is building a new File Explorer for Windows 10X with OneDrive at its heart.
Microsoft is finally developing a new modern File Explorer, and it will be preloaded on Windows 10X when it launches later this year. This new File Explorer is a simplified, lightweight explorer for browsing your OneDrive storage, and syncing files back and forth between the cloud and your local machine. It's a very early build of the new File Explorer, so hopefully, there's more to come in the future.

Full story from the WindowsCentral blog...