What is Z-index property in CSS ?

The z-index property in CSS controls the vertical position order of an elements.
An element with greater position order is always use in front & lower in back.

Z-index property:
z-index property is use always greatest position order of an element.

Syntax:-

z-index: "position-order";

Syntax Example:-

z-index: 1;

Example: HTML & CSS code

Z-index:2

Z-index:3

Z-index:1

Output of Above the Code is as below.