React is an open-source JavaScript UI library that helps developers build user interfaces with minimal stress, using a tree-like structure for organization. By comparing it to Flask, a Python microframework, this article shows how to translate a simple Flask web application to React. The process involves creating a new React application, rewriting the code in React, and adding components and props to make the UI more dynamic. The article also covers the use of CSS in React, including inline styling and separate CSS files. With these skills, developers can build scalable and maintainable applications with React.