RequireJS is a JavaScript file and module loader designed to optimize the management of JavaScript dependencies and improve the performance of web applications. By using asynchronous loading, it helps avoid issues related to script order and dependency management, resulting in faster page loads. RequireJS encourages modular development, enabling developers to structure their code into manageable, reusable components. In a browser environment, it can load JavaScript files asynchronously, and in a Node.js environment, it can be used to run JavaScript modules.