Explainers for several kinds of units proposed for inclusion in CSS (and SCSS and LESS)

• anthropometric units related to the human body and mind, which may adapt to the user to improve acessibility, e.g. tip
• real physical length units that do not depend on the display environment (and are never anchored on px)
• traditional or local typographic length units like the Didot point
• adaptive length units relating to the measures of the actual font used (like em etc.), e.g. upstroke thickness