Where can we look up which font-weights are available to specific fonts?
Most system fonts (native fonts found on most operating systems) only have
font-weights of normal (400) or bold (600).
When dealing with web fonts, we tend to have many more weights available for use. These weights can generally be found from the source where the web font was bought or procured. For example, each web font card shown on Google Fonts has a drop-down menu showing all the available weights an associated font can have.