DVI is the output format for the TeX typesetting system.
DVI intends to be a Device independent format to specify the visual layout of a document.
TeX/LaTeX can produce DVI files and these are feed to a different program to produce final graphics like a screen view, a PostScript or PDF file. DVI does not specifiy fonts the way a PDF file does and although it handles a certain machine language is not as complex as PostScript (as in Not Turing-complete).