WebUI4CSharp is a WebUI wrapper, which allows you to use any web browser as a GUI, with C# in the backend and HTML5 in the frontend.
WebUI allows you to link your console, WinForms or WPF application with a web app that runs in a web browser installed in the operating system. Originally WebUI was created to have all the UI code in the web browser and the rest of the code in your hidden C# application. However, you can also decide to have a visible C# application communicating with a HTML5 app. You can get web browser events in your desktop application, call C# functions from JS, call JS functions from C# code, execute JavaScript, etc.
WebUI4CSharp can be used console, WinForms or WPF applications for Windows.
WebUI doesn't embed a web browser in your application. It's used as a bridge between a desktop application and the web browser running an HTML5 app.