This example shows a minimal React application rendering a “Hello World” heading inside a flex-styled div. It demonstrates the basic structure of a React app, using the `React` and `react-dom` libraries to define a functional `App` component and mount it into the page’s root element via `ReactDOM.render`. The HTML file contains only a root container, while the JavaScript handles the component definition and rendering, providing a simple starting point for building interactivity or data visualizations with React.