Source: https://techcommunity.microsoft.com/t5/windows-kernel-internals/windows-sandbox/ba-p/301849

Windows Sandbox is a new lightweight desktop environment tailored for safely running applications in isolation.

How many times have you downloaded an executable file, but were afraid to run it? Have you ever been in a situation which required a clean installation of Windows, but didn’t want to set up a virtual machine?

At Microsoft we regularly encounter these situations, so we developed Windows Sandbox: an isolated, temporary, desktop environment where you can run untrusted software without the fear of lasting impact to your PC. Any software installed in Windows Sandbox stays only in the sandbox and cannot affect your host. Once Windows Sandbox is closed, all the software with all its files and state are permanently deleted.

Windows Sandbox has the following properties:

Part of Windows – everything required for this feature ships with Windows 10 Pro and Enterprise. No need to download a VHD!
Pristine – every time Windows Sandbox runs, it’s as clean as a brand-new installation of Windows
Disposable – nothing persists on the device; everything is discarded after you close the application
Secure – uses hardware-based virtualization for kernel isolation, which relies on the Microsoft’s hypervisor to run a separate kernel which isolates Windows Sandbox from the host
Efficient – uses integrated kernel scheduler, smart memory management, and virtual GPU