Virtualisation will have to be enabled at the BIOS level on the PC.
Microsoft has been looking for ways to simplify the way users log into Office and find their documents via its Office.com portal. The feature update is still blocked for a number of configurations or devices, e.g. for devices with AMD Radeon HD2000 and HD4000 graphic processor units, devices with TrendMicro security software that run older versions of the software, or devices with certain Intel display driver versions. The feature, Windows Sandbox, will be available only on the Windows Pro and Enterprise editions. In other words, this is nearly like a normal VM, where the VM uses an entirely different OS image than the one on the host, except the Windows Sandbox uses unmodified files of the operating system to save on resources. The company released a cumulative update for the version of Windows 10 in December that addressed additional bugs and issues.
The upcoming version of Windows 10 codenamed 19H1 will offer a new optional feature called Windows Sandbox.
It remains to be seen how well Windows Sandbox can be integrated into regular workflows and whether app data from the Sandbox can be saved to the host drive or not. This is what allows the "base image" that is used in a Windows Sandbox environment to be only 100MB, as opposed to several GB, which is what a new Windows installation/image would take.
Microsoft's Windows 10 October Update has had its fair share of issues, but now it's widely available for all users.
Sharing is used for memory, too; operating system executables and libraries loaded within the VM use the same physical memory as those same executables and libraries loaded into the host OS. This means that if the sandbox has a low priority thread, it can be displaced by a higher priority thread from the host. The feature is now present in Windows 10 build 18305 and should make it to Insiders soon. The sandbox virtual machine is different; its processes and threads are directly exposed to the host OS' scheduler, and they are scheduled just like any other threads on the machine.
Using the Sandbox, you can open files, infect it will all sorts of scary malware, and then shut it down. Today's build is 18305, and is packing a whole bunch of new features and changes for Insiders to test.