I am new to React and was learning how to properly use React Router with React all together. As you know, the React Router was divided into three packages: react-router, react-router-dom and react-router-native. So, both react-router-dom and react-router-native by default have react-router inside of them. The question is since both react-router-dom and react-router-native include react-router then what is the reason to have react-router as separate package?