LyX is a document processor that encourages an approach to writing
based on the structure of your documents (WYSIWYM) and not simply
their appearance (WYSIWYG).

LyX combines the power and flexibility of TeX/LaTeX with the ease
of use of a graphical interface. This results in world-class support
for creation of mathematical content (via a fully integrated equation
editor) and structured documents like academic articles, theses,
and books. In addition, staples of scientific authoring such as
reference list and index creation come standard.  But you can also
use LyX to create a letter or a novel or a theatre play or film
script. A broad array of ready, well-designed document layouts are
built in.

LyX is for people who want their writing to look great, right out
of the box.  No more endless tinkering with formatting details,
"finger painting" font attributes or futzing around with page
boundaries. You just write. On screen, LyX looks like any word
processor; its printed output - or richly cross-referenced PDF,
just as readily produced - looks like nothing else.