What are "who parameters"? (man 8 renice)

[Ottavio Caruso]

Can manual pages be more arcane and esoteric than this?

% man 8 renice

https://man.bsd.lv/FreeBSD-12.0/renice

"The following who parameters are interpreted as ..."

"-g
     Force who parameters to be interpreted as process group ID's."

"-u
     Force the who parameters to be interpreted as user names or user ID's"

"who" is underlined. Is it an acronym? I've seen this mentioned only in 
this man page on FreeBSD and NetBSD.

The OpenBSD manual page seems to to be saner:
https://man.bsd.lv/renice

-- 
Ottavio Caruso