JavaScript is a high-level, interpreted programming language that is widely used to add interactivity and other dynamic elements to websites. It is a client-side scripting language, meaning it runs directly in the user's web browser, rather than on a server. This allows for a rich and dynamic user experience without the need to constantly refresh the page. One of the most common uses of JavaScript is to change the appearance of a webpage in response to user actions. For example, changing the size of the image, changing the font, etc.