Hi R C-R,
i've never created video -- would like to to 'explain' this properly, but unfortunately dont have time now to mess around with it,
so will try answer your questions:
1. yes, the pointer is over one of the handles
2. when you press Ctrl and drag the mouse, the pointer stays where it is in relation to the point:
a. the whole package (pointer, point, handles) moves as you drag
b. when you release Ctrl key, the only difference to position #1, is that the point is in a different place, if you now drag again, the handles can still be moved, exactly same as before step #2
So the only reason for this is to be able to move a point on the fly:
as I said above, particularly when 'tracing' a bitmap, this is a huge timesaver (particularly if you have to draw as lot, as I have to do on occasion)
I hope that's clearer, and that you can now see why it would be of use to some people.
I'll have a quick look on Youtube, see if I can find a video displaying this.