Let's talk about Event Propogation
Blue Child - Seems like you shouldn't be able to drop onto me, because my Red parent implements the drop and dragover handlers and I don't, but you can drop here.
Red Parent - Me, this level, has the drop and dragover handlers necessary to be a drag target.
Green Grandparent - Dropping here doesn't work, because the drop-associated event handlers are defined on my child (the Red Parent level).
Drag the button div below over the green, red, and blue divs. Watch the console.
There are 3 elements inside this div, all different background colors.
If you click on a element inside an element that has event handlers, you sometimes want it to pass the event up.
The Purple div is the only one with a click handler, but you assume you could click anywhere inside it and get the event.