This is really different,
React is view library;
and Rxjs is reactive programming library for javascript.
You can use Rxjs inside react view but in reactjs, people usually use a library like Redux, flux, mobx or relayjs (if they use graphql) for data flow.
ReactJs is a view library UI. ReactiveX or rxjs is a concept, methods or patterns for asychronous programming.
ReactJS In the simple and popular term, React is the V (View) in MVC (Model/View/Controller).
React is a JavaScript library (from Facebook) that is used to render views (for example, HTML pages) dynamically based on some state, which is often in the form of data. React then updates the generated views whenever the original state changes. React is a small but powerful library, with the power being more in the concepts than in the implementation.
React is a javascript library for building user interfaces whereas RxJS is a javascript library for reactive programming using Observables.
https://stackoverflow.com/questions/41670972/what-is-the-difference-between-reactjs-and-rxjs