This new feature, that has been present & working in the Insider builds, is going to be included in the next version of win10, due out this March [or April, or May if Microsoft repeats 2018's fiascos]. The end result is much like using Shadow Defender, Time Freeze, & other virtualization apps, but the tech behind it is different. Windows Sandbox sort of walls off the hardware & Windows resources that are used, rather than redirecting all new hard disk writes to a separate file that's then discarded when Windows restarts [the way apps like Time Freeze work]. It uses some tech from Hyper-V, Microsoft's VM [Virtual Machine] software, and it uses Windows Remote Access. Sandbox is not a VM, with separate host software running a full version of Windows, but it almost looks like it is, with a clean win10 desktop running in a window.
The Hyper-V tech Sandbox uses makes use of the CPU's virtualization features, so just like Hyper-V itself, you can't have Sandbox installed & run VirtualBox -- they're incompatible. You install Sandbox much the same way you install Hyper-V, in the added features portion of Control Panel -> Programs and Features -- it does require a restart.
Microsoft has been going down this road for a while now, with Device Guard, Application Guard etc., and they've also been working with Linux, Android, & most recently, software supporting ARM hardware, all in Windows. They're also facing a bit of a dilemma -- to make the parts of Windows that users deal with more like Android, with easy upgrades etc., they need to slim Windows down, getting rid of code that's been in there since Windows 95. If their store had caught on, it would have gone a long way towards solving that problem, but it never came close enough to even register as a blip on any graph.
SO a lot of people, e.g. Thurrott, feel that win10's Sandbox is some sort of stepping stone -- it's not the tech that Microsoft's ultimately after, but it's usable tech that they've developed as they work towards whatever final goal. And it is usable, today if you set a copy of win10 to receive Insider builds in the fast ring -- the much easier to live with Slow ring hasn't been receiving much [if any] attention for a while now. The good news is that the upgrade to the latest Insider build is less painful and much faster than even the Fall update that was released late last year. The bad news is that, besides being beta code, & thus glitch prone, it might be a bit much to upgrade win10 once a week, & perhaps more often as it nears release. Maybe the slow ring will return, with it's easier once a month on average upgrade schedule, but it hasn't yet.
petri[.]com/how-to-enable-windows-sandbox
