A typeface can have various degrees of stroke thickness which has to be consistent across the glyphs of the same font style. It is the font’s weight.

The few centuries of typeface development, mainly in the Latin world, brought us a standardized naming for weight values. They serve more as a way to identify each style within a typeface family rather than being a standard to follow, as styles descriptions are different from one culture to another.

In web design, each weight has a specific CSS code.