If you want to know more about nroff (which is what man calls when you want text output, I believe), then you could e.g. read https://www.nesssoftware.com/home/

If you want to know more about nroff (which is what man calls when you want text output, I believe), then you could e.g. read https://www.nesssoftware.com/home/mwc/doc/coherent/manual/pdf/nroff.pdf https://www.nesssoftware.com/home/mwc/doc/coherent/manual/pd..., or https://www.quut.com/berlin/ms/troff.html https://www.quut.com/berlin/ms/troff.html. It's terse, like nroff itself. I think people tried to convert man pages by redefining the macros and then let nroff produce the output.