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.
Groff can also be used to format man pages. If you are going to use groff with the X Window System, you will also need to install the groff-gxditview package.