what is the different between z index and multiple background?? is it same or what?

Question

im got confused with this thing

Answer 1

z-index is the overlapping priority of an element. If you put many elements on top of a specific one but you want this to appear on top you can increase its z-index.

Answer 2

For multiple background, order is defined in the background-image property:

background-image: url("most-top-image.url"), url("image.url"), url("most-bottom-image.url");

Answer 3

and what about multiple background?

Answer 4

multiple background can overlap each other and also merge their color effects
but z index just overlaps multiple colors (just colors)