Tauri is a framework for building tiny, blazing fast binaries for all major desktop platforms. Developers can integrate any front-end framework that compiles to HTML, JS and CSS for building their user interface. The backend of the application is a rust-sourced binary with an API that the front-end can interact with.
The user interface in Tauri apps currently leverages Cocoa/WebKit on macOS, gtk-webkit2 on Linux and MSHTML (IE10/11) or Webkit via Edge on Windows. Tauri uses (and contributes to) the MIT licensed project that you can find at webview.