React VR is based on React, a framework that allows web pages and interactive User Interfaces to built by declaration instead of programming. You build views for each state in the application, and then React will use the correct components to display that application.
Declarative views make your code easier, more robust, and easier to modify and debug.
Components use the Object-Oriented concept of encapsulation, meaning they are self-sufficient and manage their own state. You then take these components and use them to make complex UIs.
React was first used with Facebook's newsfeed in 2011. It was made open-source in March, 2015.
You can find more details about React at https://facebook.github.io/react/.