Let's talk about Event Propogation

Event Propogation is really important in Javascript.
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.

Drag me!

Click Me!

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.