An event listener is a programming construct that waits for a specific event to occur, such as a user clicking a button or pressing a key. When the event happens, the listener triggers a predefined function or action, allowing developers to create interactive applications. Event listeners are commonly used in web development to enhance user experience by responding to user actions. In many programming languages, including JavaScript, event listeners are attached to elements like HTML buttons or DOM elements. They help manage events efficiently, enabling developers to separate the logic of handling events from the rest of the code, making it easier to maintain and update applications.