It a set of scripts from the create-react-app starter pack. create-react-app helps you kick off projects without configuring, so you do not have to setup your project by yourself. react-scripts start sets up the development environment and starts a server, as well as hot module reloading.
With npm:
npx create-react-app my-app
cd my-app
npm start
It will create a directory called my-app inside the current folder. Inside that directory, it will generate the initial project structure and install the transitive dependencies:
my-app
├── README.md
├── node_modules
├── package.json
├── .gitignore
├── public
│ ├── favicon.ico
│ ├── index.html
│ └── manifest.json
└── src
├── App.css
├── App.js
├── App.test.js
├── index.css
├── index.js
├── logo.svg
└── serviceWorker.js
└── setupTests.js
No configuration or complicated folder structures, only the files you need to build your app. Once the installation is done, you can open your project folder