The "onChange" event is a feature commonly used in programming, particularly in web development. It triggers a specific action when the value of an input element, such as a text box or a dropdown menu, changes. This allows developers to create interactive applications that respond to user input in real-time, enhancing the user experience. In frameworks like React or Vue.js, the "onChange" event is often used to update the state of a component. When a user types in a field or selects an option, the event captures this change, enabling the application to react accordingly, such as displaying updated information or validating input.