JavaScript is a versatile, high-level programming language primarily used to create interactive effects within web browsers, enabling dynamic content and user engagement.
React is a JavaScript library developed by Facebook for building user interfaces, particularly single-page applications, by breaking down the UI into reusable components that efficiently update and render as the data changes.
Together, JavaScript and React empower developers to build responsive and interactive web applications with a smooth user experience.
I highly recommend the https://react.dev/learn/tutorial-tic-tac-toe tutorial.