JavaScript is a versatile, high-level programming language primarily used for client-side web development. As a core technology alongside HTML and CSS, JavaScript enables the creation of dynamic and interactive web pages. It is supported by all major web browsers, allowing developers to add functionality and interactivity to websites. JavaScript is an object-oriented language that supports event-driven programming, making it suitable for creating responsive user interfaces. Its widespread use in web development, both on the client and server sides (Node.js), highlights its importance in building modern, feature-rich web applications.