css vw or % code example

Example 1: what is css vh

CSS VH unit Property
Viewport Height ( vh ) 
– A percentage of the full viewport height. 10vh will resolve to 10% of the current viewport height. Viewport Minimum ( vmin ) 
– A percentage of the viewport width or height, whichever is smaller.

Example 2: what is em in css

'em' units for the font-size property will be relative to the'font-size of the parent element'.
'em' units on other properties other than font-size will be relative to the
font-size of the current element. 'rem' units sizes will always be relative 
to the font-size of the root html element.