JavaScript is a high-level, just-in-time compiled, object-oriented programming language used to make web pages interactive. It is an essential technology of the web, alongside HTML and CSS, enabling dynamic content, form validation, event handling, animations, and more. JavaScript is executed on the client side by web browsers, providing immediate feedback to user interactions without needing to reload the page. It supports various programming paradigms, including functional, imperative, and event-driven programming. JavaScript frameworks and libraries, such as React, Angular, and Vue.js, further enhance its capabilities for building complex web applications.