DocTeX mode is for editing buffers containing self-documenting LaTeX code that uses the doc package, including the ltxdoc document class. DocTeX mode was designed to be significantly more useful than the alternatives provided by standard Emacs and AUC TeX (AUC TeX has since caught up in this regard). SwifTeX mode is for editing buffers containing normal LaTeX files and provides an alternative to the LaTeX modes in the standard Emacs distribution and in AUC TeX.

The author is Matt Swift.