Answer 1

Probably you mean capturing instead of propagation?

Event bubbling or capturing are terms used to describe the order in which events like click events are to be handled.

bubbling: bottom-up
capturing: top-down

Consider the following where you have three nested Div elements:
<div>--
<div>
<div><\div>
<\div>
<\div>

Suppose you clicked on 3rd div and you want to handle clicks on 3rd div first and then 2nd div etc (remember that 3rd div and 2nd div are nested in 1st div, so a click in 3rd div also counts as a click in the 1st), then you have to use bubbling. The other way around would need the capturing propagation type.