Groff is a document formatting system. Groff takes standard text and
formatting commands as input and produces formatted output. The created
documents can be shown on a display or printed on a printer. Groff's
formatting commands allow you to specify font type and size, bold type,
italic type, the number and size of columns on a page, and more.

You should install groff if you want to use it as a document formatting
system. Groff can also be used to format man pages. If you are going to
use groff with the X Window System, you'll also need to install the
groff-gxditview package.