4 - ASP.NET Controls Events and Event Handlers
ASP.NET controls can support multiple events. For example ASP.NET button control supports the click event, command event, Load events etc. Event handler will handle the events that is generated by a control. The event handler can be added in different way, for example if you double click on a button control, the default event handler will be added automatically. You can also use the property window to add event handler to a control's event.