The JavaScript programming language is often used for creating dynamic web applications. It enables developers to implement interactive features on websites, enhancing user experience. JavaScript works seamlessly with HTML and CSS, allowing for the creation of rich client-side interfaces. Furthermore, with frameworks like React and Angular, it simplifies the development of complex applications. Node.js, a JavaScript runtime, allows for server-side capabilities, enabling developers to use a single language across both client and server environments, contributing to greater efficiency and faster development processes.