1.Clicking the mouse.
2.Pressing a key on the keyboard.
When you click on a button it is recognized as an event by the button.
A calculator (Provided in your Windows) shown in figure is the perfect example of events and their quick responses.
Clicking on a number Button will display a particular number in the text Box.Some of events like methods require additional information in the form of arguments.
Click event does not requires arguments whereas DragDrop event requires arguments as shown in example:
Public Sub Command1_Click()
Public Sub Commnand1_DragDrop(Source As Control,X as Single,Y As Single)