DOM Events are sent to notify code of interesting things that have taken place. Each event is represented by an object which is based on the Event
interface, and may have additional custom fields and/or functions used to get additional information about what happened. Events can represent everything from basic user interactions to automated notifications of things happening in the rendering model.
This website offers a list of events that can be sent; some are standard events defined in official specifications, while others are events used internally by specific browsers; for example.