Repeated Elements in Typeface design


I stumbled upon the Typeface Design Characteristic "Repeated vs. no Repeated Elements" which is supposed to influence font-weight. Can somebody please explain this design characteristic as well as why it influences weight? It would be great to have other examples to look at.

Attached is an image of one example of the design characteristic.


What is font-weight for??

Dear all,

usually, we can set font-weight info in OS/2 table.
Then, what is for the usage of font-weight?

whenever I searched on the info, I can get only css-related or xml, html-related usages..
except those usages, are there any possible usage?
is there any application that uses the info?

if anyone knows it, please let me know..