Now that you have understood the purposes of folder structure and base theme’s source files, it’s not over yet! Next, we will guide you with how to execute these files. The normal React application created using create-react-app renders the app using the render() method. But the base theme is different. If you open the index.tsx file, you wouldn’t find a call to the render() method. Instead, you should see a call to the App() method. 
import { App } from 'experro-storefront';
// ...other imports

App({
  templates,
  widgets: WidgetConfig.widgets,
  components,
  singleDataModelsToPrefetch: ['header'],
  routes: Routes,
  headerComponent: components.Header,
  footerComponent: components.Footer,
});

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Where is This Method Imported From?

This App() method is imported from experro-storefront package. The experro-storefront or Experro Storefront is the engine responsible for rendering the base theme and providing many helpful features. As we go through the documentation, we’ll discover more about these features provided by Experro Storefront. However, let’s begin with one to get started. Experro Storefront provides two default environments to work with. Let’s get you familiar with these development environments in the next section.