The groff-x11 package contains the parts of the groff text processor package
that require X Windows System. These include:
o Gxditview displays the groff text processor's output on an X Window System
display. If you are going to use groff as a text processor, you should
install gxditview so that you preview your processed text files in X.
o xtotroff converts X font metrics into groff font metrics
o eqn2graph converts EQN equation descriptions to bitmap images
o grap2graph compiles graph description descriptions to bitmap images
o pic2graph compiles PIC image descriptions to bitmap images

You'll need to install the groff package and the X Window System.