https://arstechnica.com/gadgets/2018/02/windows-10-s-becoming-a-mode-not-a-version-as-microsoft-shakes-up-its-pricing/

With the next big update to Windows 10, version 1803, Microsoft is making some big changes to how it sells the software to OEMs. The biggest casualty? Windows 10 S—the restricted version of Windows that can only run apps from the Store—is going away.

Currently, Windows 10 S is a unique edition of Windows 10. It's based on Windows 10 Pro; Windows 10 Pro has various facilities that enable system administrators to restrict which software can be run, and Windows 10 S is essentially a preconfigured version of those facilities. In addition to locking out arbitrary downloaded programs, it also prevents the use of certain built-in Windows features such as the command-line, PowerShell, and Windows Subsystem for Linux.