What is the use from " z-index" in CSS?

<style>

#class name or id name{

z-index:99999;

}

</style>

It is positioned element that use to overlap the two div(boxes).

z-index is used to position the elements on top, basically like stacking the elements. Those elements with higher z-index value will be on top. 

iam web desighner not web develper

An element with greater z-index number is always in front of an element with a lower z-index number.

z-index is a css property that enables the layering of elements (in front of, behond)

The z-index property specifies the stack order of an element.

simply the order of elemnt which win will apear first look like layers and you choose to apear first

z-index is a css property that allows to position an object/element in front/behind of other

z-index is basically to give significance if we have multiple divisions overlapping.The one with greater z-index will stand out more than the other

z-index is responsible for setting layers and selecting its order on css