According to Microsoft's website, "Windows 10 Education in S mode is designed to give schools the familiar, robust, and productive features they count on from Windows in an experience that's been streamlined for security and performance in the classroom and built to work with Microsoft Education." PC's with Windows 10 in S mode can only install applications from the Microsoft Store and you can only browse the web using Microsoft Edge and uses the Bing search engine. These restrictions eliminate malware and spy applications from being installed on your computer and improve processing speed.
The Microsoft Store includes all your favorite Microsoft apps and Microsoft-verified apps, such as Office, Evernote, Spotify, KNFB Reader, Read&Write, Narrator, and Magnify. This is similar to iOS devices which only allow applications from the App Store. Running Windows 10 in S mode is optional (and free!). Users can choose to move out of Windows 10 S mode; however, once you leave S mode, you cannot go back. Third party apps such as JAWS, NVDA and ZoomText are not available in the Microsoft Store.
The audio described video by Microsoft below introduces Windows 10 Education in S Mode.