Xdvi allows you to preview the TeX text formatting system's output
.dvi files on an X Window System.
If you are installing tetex and you use PlainTeX or you are using DVI files,
you will also need to install tetex-xdvi which allows you to view DVI files.
Consider installing tetex-dvips (for converting .dvi files to PostScript format
for printing on PostScript printers), and tetex-latex (a higher level formatting
package which provides an easier-to-use interface for TeX). If you are
not a TeX expert, you will probably also want to install the tetex-doc
package, which contains documentation for the TeX text formatting