What does it mean about"html event"?

Does anyone know about html event? What is its mean? And could you show me an example how to use it?

Thanks

This should help (http://www.w3schools.com/html/html_eventattributes.asp)

There is also this set of events as well:

DHTML Events (http://msdn.microsoft.com/workshop/author/dhtml/reference/events.asp)