Pywebview uses native GUI for creating a web component window: WinForms on Windows, Cocoa on Mac OSX and Qt4/5 or GTK3 on Linux.
You can use pywebview either with a lightweight web framework like Flask or Bottle or on its own with a two way bridge between Python and DOM. It gives you power of web technologies in your desktop application, hiding the fact that GUI is browser based.
Pywebview is a lightweight cross-platform wrapper around a webview component that allows to display HTML content in its own native GUI window.