This example demonstrates a minimal React application that renders the text "Hello React!" centered on the page. It uses React 16.10.0 and ReactDOM to mount a functional component into a div with the ID "root". The component returns a simple div with a CSS class that sets a large font size and text alignment. The page loads the compiled bundle.js file, which contains the transpiled JavaScript code, and relies on the UMD builds of React and ReactDOM from a CDN.