Their sequence of firing is:

1)MouseDown
2)Click
3)MouseClick

Differences:

MouseDown:
1)It helps us to identify which mouse button was pressed(ex: left,middle, right)

2) Does not fire through a keyboard

3)can also be used to give coordinates(X and Y coordinates where the mouse

was pressed)

Click:
1)we cannot identify the mouse button that was pressed

2) Does fire through keyboard (enter, spacebar keys for example)

3)Does not give co-ordinates

MouseClick:
1)Fires through the default button(Left Button)

2)Does not fire through keyboard.

3)Gives coordinates where the Mouse was clicked.


source:http://www.dotnetfunda.com/interview/exam4035-difference-betweem-mousedown-clickmouseclick-events-in-windows-applicatio-.aspx