The groff package provides compatible versions of troff, nroff, eqn,
tbl, and other Unix text formatting utilities.

Groff is used to "compile" man pages stored in groff or nroff format
for different output devices, for example, displaying to a screen or in
PostScript(tm) format for printing on a PostScript(tm) printer. Most
programs store their man pages in either /usr/share/man/ or
/usr/X11R6/man/.