Microsoft is trying something new with Windows 10 S next year.
Windows 10 S was originally launched as a dedicated operating system for convertibles and laptops targeting students, though starting next year, it will become a special “S Mode” for versions of Windows 10. Neowin spotted last month that Microsoft wants to offer this “S Mode” on PCs running Windows 10 Home, Enterprise, and Pro. However, now, Microsoft itself has confirmed the decision.
Microsoft VP Joe Belfiore revealed on Twitter that "10S will be a ‘mode’ of existing versions, not a distinct version." It will lock down Windows 10 so that the system can only run apps from the Microsoft Store. It should function in the same way as the Windows 10 S operating system that's currently available. But it's unclear if it will be available free of charge, and we likely won't know until 2019.
We use Win10S as an option for schools or businesses that want the 'low-hassle'/ guaranteed performance version. Next year 10S will be a "mode" of existing versions, not a distinct version. SO … I think it's totally fine/good that it's not mentioned.March 7, 2018
Windows 10 S is described as a fully-functional version of Windows that is designed to run smoothly on all hardware. Microsoft hasn't revealed exactly what the S stands for, but said that its evolved from features that teachers have asked for - hence the education tie-in. The big catch with Windows 10 S? You can't download apps online and install them, so the version is effectively sandboxed.
You can learn more about the software from here.