EventArgs

The "sender" argument is the object that raised the event. The EventArgs argument is extra information passed to the event.
So if u clicked a button, then the sender would be the button that u have clicked.

e.g:-
public event EventHandler<EventArgs> Clicked;
Clicked += new EventHandler<EventArgs>(task_Clicked);

void taskViewControl_TaskClicked(object sender, EventArgs e)
{//functionality that you want to perform here
}