TeX is a typesetting program designed for high-quality composition of material that contains a lot of mathematical and technical expressions. It has been adopted by many authors and publishers who generate technical books and papers. It was created by Professor Donald Knuth of Stanford University, originally for preparation of his book series "The Art of Computer Programming".

TeX has been tailored for and installed on almost every platform (computer + operating system) that one can imagine, and is available as freeware, shareware and commercial implementations.

It does not require applications like PageMaker, Quark Express, Fontographer or FontLab. A TeX system can stand on its own, provided all the fonts one needs are available. TeX uses only the metrics, and produces a "device independent" output file – .dvi – that must then be translated to the particular output device being used (an imagesetter, laser printer, inkjet printer; in the "old days" even daisy-wheel printers were used). The DVI translator actually accesses the font shapes, either as bitmaps, Type 1 fonts, or pointers to fonts installed in a printer with the shapes not otherwise accessible.

PostScript is one of the most popular "final" output forms for TeX; in this respect, TeX is comparable to Quark, for example.

One of the major areas where TeX will hold its own over the next few years is as a "back end" to SGML and XML systems, where no human intervention is expected between data input (structured, not WYSIWYG) and removing the output from the printer or viewing it on a screen. Granted, this isn't "creative" in the sense most often discussed, but it's still important to the readability and usefulness of such documents that care is taken with the design and typography, and the flexibility and programmability of TeX makes that possible.