React is a declarative, efficient, and flexible JavaScript library for building user interfaces.Your components tell React what you want to render – then React will efficiently update and render just the right components when your data changes. Here, ShoppingList is a React component class, or React component type.
A React Native app is a real mobile app. With React Native, you don't build a “mobile web app”, an “HTML5 app”, or a “hybrid app”. You build a real mobile app that's indistinguishable from an app built using Objective-C or Java. React Native uses the same fundamental UI building blocks as regular iOS and Android apps.
[More info][1]

[1]: https://medium.com/@alexmngn/from-reactjs-to-react-native-what-are-the-main-differences-between-both-d6e8e88ebf24

ReactJS is a core framework, meant to build component isolated based on reactive pattern, you can think of it as the V from MVC, although I would like to state that react does brings a different feel, specially if you are less familiar with reactive concept.
ReactNative is another layer that is meant to have a set component for Android and iOS platform that are common. So the code looks basically the same as ReactJS because is ReactJS, but it load natively in mobile platforms. You can also bridge more complex and platform relative API with Java/Objective-C/Swift depending on the OS and use it within React.