This project accompany's my LogRocket post on an intro to React Native with macOS.
The project in the ReactNativeFirstProject folder is a React Native project generated with the Expo CLI.
The project in the calculator folder is a modified version of the React Native calculator example here. This project is specifically a React Native for macOS calculator.
To learn more I recommend reviewing the official documentation for React Native here as well as the Microsoft site on React Native for macOS here.