So what did create-react-app do when we ran the command? First of all, it created a folder structure for the application. It then created a file called package.json. This file holds a record of all of the main dependencies that create-react-app uses, along with some other meta information about the project. You can see that along with the React library installed at the latest version available, there's also a React DOM package. 

To run a React application, these are the only dependencies you actually need. The react-scripts dependency is used by create-react-app to execute several steps with one command. You can see in the script section the start, build, test, and eject all called react-scripts as part of their command. There are also three testing dependencies installed which, if we're going to use testing in our application, provide us with the basic testing tools needed. 

The package-lock.json file contains information about the dependencies of these dependencies. And the node-modules folder contains all of the dependency code. The public folder is where we find our index.html file. This is the file that the browser uses as a base for the file that is compiled when we run or build our application. The public folder is where we found our index.html file. 

This is the file that the build process uses as the base for the file that is created when we run or build our application. The src folder is where the developer will do most of their work. It contains some config files like setupTests and serviceWorker, and also the fileIndex.js. 

This is important as it is where the JavaScript in our application will start to execute. I'll explain more about the contents of this file in another video. But essentially it tells React where to put our application, and how to build it. It has a CSS file that is attached to it, so any global styles could be put in there. CSS files are bundled and minified as part of the build process too. The app.js file is a React component. It is a mixture of JavaScript and HTML, which may look strange if it's the first time you've seen it. But believe me, you'll soon get used to it. 

Essentially we've got a JavaScript function that eventually returns the representation of the DOM element. This is what React will use to render your UI. Again, this has a CSS file attached to it. And again, any styles you want to propagate through your application can be put in here. The final file we're going to look at is the App.test.js file. create-react-app comes with Jest baked into the setup. And this is a skeleton testing file. We'll get into testing in other videos. 

The final file to point out is the README.md file. If we open this, we can see explanations for the script commands. npm start runs and hot loads our application. npm test starts the test runner and runs the tests, which again, hot load if we make changes to them. npm run build which readies the application for deployment. And npm run eject, which does things you might regret later.