TeX is a program that can typeset text. Unlike Microsoft Word, TeX is a batch text processor. You prepare material with the editor of your choice (my choice) and run TeX to produce output.
In our days, the idea of batch text processing sounds weird, something for geeks. With Microsoft Word, you can see immediately the result. And that's one of Word's problems: what you see, is all you got.
A second problem with Word is the time it takes to do anything else than typing plain text. Why do we see so few documents with cross references? An index? I agree that many things possible in TeX are also possible in Word. But bug ridden, virus prone Word easy to use?
And finally, you worked so hard on your document. Why not use a tool to make something beautiful as well. We, humans, find a beauty in mathematics and mathematical properties. Maybe you have heard of the golden section. The golden section is an irrational mathematical ratio, expressed as 1.61803398:1. (Irrational) mathematics can please the senses with its emotional rationality. Through the power of TeX text batch processing you can mark up your document with such mathematical rigour. Which other tool makes it as easy as TeX to specify that this part of a document is a third of that part? That only 66% of a page can be filled with figures? TeX documents have a mathematical naturality to look beautiful.
Let's end this discussion with a word from D.E. Knuth, TeX's author:
I never expected TeX to be the universal thing that people would turn to for the quick-and-dirty stuff. I always thought of it as something that you turned to if you cared enough to send the very best.
(interview in advogato)
TeX documents look good, even with a bad macro pacakge. LaTeX is the most widely used macro package for TeX, but not the best. Almost 10 years old ConTeXt is a modern, easy to use, macro package to create beautiful hard-copy and on-screen, interactive documents.
I feel grateful to be able to use TeX and ConTeXt all day creating software designs.
Because LaTeX is so well known, people find it sometimes difficult to switch. I've written a guide for LaTeX users to make this switch easy: "LaTeX in proper ConTeXt". The many examples show first the LaTeX code and next the corresponding ConTeXt code. This document has never been as complete as I had wanted it to be, but despite its shortcomings many people have reported that it had been useful for them.
I use Emacs to write ConTeXt code. If you do as well, I suggest you install AUCTeX, a great package that allows you to edit TeX, LaTeX and ConTeXt source with ease.
After you have installed auctex and loaded a document, just type M-x context-mode to enter ConTeXt instead of LaTeX.