Что стоит в CSS
em = relative to parent element fontsize
rem = relative to root fontsize of html
QuietHumility
em = relative to parent element fontsize
rem = relative to root fontsize of html/*vh viewport height and vw viewport width*/
/*example*/
div
{
display: inline-block;
height: 100vh; /*THis will set height equal to the height of windows*/
width: 100vw/*This will set width equal to width of windows*/
}