Windows Sandbox allows you to run Windows 10 in a virtual machine where anything you do in it does not affect the main operating system. Sandbox can be used to test suspicious programs, web extensions, or web sites for malware or malicious purposes without having fear that it could affect your data or programs. Windows 10 version 1903 also introduces enhanced control over the installation of Windows updates and an improved troubleshooting experience. The update introduces a true “Light Theme”” that turns apps
Source: Action Center