React.js is the heart of React Native, and it embodies all React’s principles and syntax, so the learning curve is easy. The platform is what gave rise to their technical differences. Like the browser code in React is rendered through Virtual DOM whileReact Native uses Native API’s to render components on mobile.
Useful Links:
http://www.cognitiveclouds.com/insights/what-is-the-difference-between-react-js-and-react-native/
https://stackoverflow.com/questions/34641582/what-is-the-difference-between-react-native-and-react