What is ReactJS?
It uses JSX as its primary syntax, which is a HTML+JS+CSS combination developed by Facebook.
What is React Native?
React Native is a mobile applications development framework built on top of ReactJS, that allows you to build performant, native mobile applications by writing code that is very similar to pure React.
Are React Native and React interchangeable?
For short - no.
Firstly, you cannot use React Native without also using React. Secondly, React Native is not a tool that can be used on the web (even if third party efforts do exist) or in SSR.