JavaScript is a programming language that is primarily used to create interactive front-end web development. It can also be used to create server-side applications using technologies like Node.js. JavaScript allows developers to create dynamic user interfaces, validate user input, create animations, and perform other types of interactive logic on a web page. It is often used in conjunction with HTML and CSS to create complex web applications. JavaScript code is executed by the web browser and can interact with the Document Object Model (DOM) of the web page, allowing the web page to respond to user actions, such as clicks and form input. It is one of the most widely-used programming languages on the web and is supported by all major web browsers.