TeX's greatest strength (besides being free) is its
portability. With most other publishing applications, you're confined to Windows or the Mac OS. TeX on the other hand, runs on Linux, Windows, MacOS, and other operating systems. And you don't need an ultra-fast box with loads of memory and lots of hard drive space in order to get publishing.
The TeX input files aren't in some proprietary format the can only
be read by the application that created them. They're straight
text. You can edit TeX documents using any text editor, like Notepad, SimpleText or Emacs. Even the final output is readable on multiple operating systems.
Like the raw input files, DVI files can be viewed and printed
on any platform without a loss of formatting. You only need the proper
fonts, which you already have - they come with any TeX system. The same applies to TeX files that have been converted to other formats, like Postscript, PDF, or HTML.
If there are any errors during typesetting, TeX notes the errors and stores them in a log file. This log file will help you quickly track down and fix any problems that exist in your input file.
Unlike, for example, Microsoft Word (whose format changes with each release), TeX is stable. The format of TeX source and output files aren't likely to change
between now and the year 2067. You can use documents produced with TeX now and in the future.
Considering the program's roots, it's not surprising that TeX is practically unsurpassed in its ability to typeset mathematics. The results you get are far better than what you'd get with applications like Equation Editor (bundled
with Microsoft Office) or even a specialized program like Mathematica.
Getting Information
Information about TeX is freely available over the Internet. There are a number of Web sites containing a wealth of TeX related documentation. Then there's the
TeX User's Group (TUG), devoted to spreading the TeX gospel. The comp.text.tex newsgroup contains a lot of useful information and gives you access to a number of TeX gurus.