Units (px, rem, em, %, vw, ch)

Also written: rem, em, vw, vh, ch, units

CSS length units. `rem` is relative to the root font size, `em` to the element's own font size, `%` to the parent's size, `vw`/`vh` to 1% of the window's width or height, and `ch` to the width of a "0". `rem` is the best choice for text because it grows with the visitor's browser font-size setting.