Bold font weight.
Bold font weight. Same as 700.
MDN
One font weight darker than the parent element (among the available weights of the font)
One font weight darker than the parent element (among the available weights of the font)
MDN
One font weight lighter than the parent element (among the available weights of the font).
One font weight lighter than the parent element (among the available weights of the font).
MDN
Normal font weight.
Normal font weight. Same as 400.
MDN
The font-weight CSS property specifies the weight or boldness of the font. However, some fonts are not available in all weights; some are available only on normal and bold.
Numeric font weights for fonts that provide more than just normal and bold. If the exact weight given is unavailable, then 600-900 use the closest available darker weight (or, if there is none, the closest available lighter weight), and 100-500 use the closest available lighter weight (or, if there is none, the closest available darker weight). This means that for fonts that provide only normal and bold, 100-500 are normal, and 600-900 are bold.
MDN