They list some potential use cases on their GitHub page:
- Write a cross-platform GUI entirely in CSS/HTML/JS
- Write a game using Babylon.js and make EmbedIO your serve your code and assets
- Create GUIs for Windows services or Linux daemons
- Works well with LiteLib – add SQLite support in minutes!
- Write client applications with real-time communication between them
If you’re interested, then take a look at their web page for more information.