Windows 10 S is a new operating system from Microsoft aimed at the education market. All it can run is Microsoft Edge and Windows Store Apps. It's basically Microsoft's answer to a Chromebook.
Last week, Microsoft released the ISO file for the Fall Creators Update. Interestingly, Windows 10 S was included in the standard ISO, so I decided to spin up a Virtual Machine and see what I could find.
Once you have installed, it will take you through the default setup procedure for Windows 10. It will ask for your region, keyboard layout etc. Like any other time you install Windows 10, it will ask you to sign into either Azure AD (Company Microsoft Account) or with a Standard Microsoft Account. If you don't have a Microsoft Account or you would rather not to use one then you can do that too.
After the setup has completed, you get a fairly standard Windows 10 desktop.
When you try to install any apps from outside the Windows Store then you'll be greeted with this message basically prompting you to upgrade to Windows 10 Pro.
Should I install Windows 10 S on my primary computer?
No. Only if you are 100% sure that all you will do is use Microsoft Edge for very light browsing.
If you would like to test Windows 10 S out for yourself then you can do so by checking out this tutorial from BetaNews. Make sure you do it on a VM and not on your primary machine.