what is Z-index in css?

The stack order of an element is specified by the z-index property. A higher stack order element is always in front of a lower stack order element.

• The CSS property known as Z Index (z-index) specifies the hierarchy of overlapping HTML elements. A higher index element will be positioned above a lower index element. Note that only positioned items can use the Z index ( position:absolute , position:relative , or position:fixed ).

z index is called height (if we need to learn shortly)

Z-index 0: 0th layer

Z-index 1: 1st layer

Z-index 2: 2nd layer respectively

If there are too elements in your page overriding in the same place, the z-index defines the item to be visible to user (the higher the z index more visible to the user)