React

React is a JavaScript-based UI development library. Facebook and an open-source developer community run it. Although React is a library rather than a language, it is widely used in web development. The library first appeared in May 2013 and is now one of the most commonly used frontend libraries for web development.

ReactJS is one of the most popular JavaScript libraries for mobile and web application development. Created by Facebook, React contains a collection of reusable JavaScript code snippets used for user interface (UI) building called components. It's important to note that ReactJS is not a JavaScript framework.