When an event occurs, you can create an event handler which is a piece of code that will execute to respond to that event. An event handler is also known as an event listener. It listens to the event and responds accordingly to the event fires.
An event listener is a function with an explicit name if it is reusable or an anonymous function in case it is used one time.
An event can be handled by one or multiple event handlers. If an event has multiple event handlers, all the event handlers will be executed when the event is fired.