CSS

what does em stand for in css

em = relative to parent element fontsize
rem = relative to root fontsize of html

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.

em in css

Relative Units: changes upon screen measurements. 
n % => counts on parent elements, for example if we have a parent of 500 px, so the 50% will be 250px
n vw	=> 1% of widths, total pixels
n vh	=> 1% of heights, total pixels.
vmax	=> maximum of height or width
vmin	=> minimum of height or width viewport
n em 	=> n x (parent element’s font size) 
n rem 	=> n x (HTML’s font size)