TeX was written in the 70's ;-) The main reason for using TeX is if you want to typeset a document that will be "photo-ready" for a print publication. Quite f

TeX was written in the 70's ;-) The main reason for using TeX is if you want to typeset a document that will be "photo-ready" for a print publication. Quite frequently it is for typesetting scientific papers (which is why it is popular with academics). Like I said, TeX is a typesetting language. It is literally a programming language that takes typesetting programs (including the data) and outputs an exact photo-ready output. It's very easy to convert the photo-ready output to a PDF, or a PNG, or GIF, SVG, etc. Because TeX is a programming language, you can write macros (there are no functions in TeX). These macros work on input you give it. In the old, old days, someone would create a set of macros for typesetting documents for each of the major journals and publications you might want to publish to. Eventually, a guy name Leslie Lamport wrote a whole set of really good macros called LaTeX that would allow you to write documents in a consistent way for a whole bunch of different types of publications. That way you could minimally change the document and resubmit it to a different publisher. So why do people still you TeX? There are two main reasons: First because there is still a need for very high quality print output. TeX is special in that it has perfect algorithms for doing things like line breaking, kerning, etc, etc, etc. The output of TeX is dramatically better than just about any other piece of software. It's insanely better than any word processor will output and there are probably only a handful of desktop publishing packages that are even close. If you need absolutely perfect print output, then TeX (and LaTeX) are a really good fit. The other reason for using LaTeX (not so much TeX, because typesetting documents in TeX is almost insane: I used to do it for fun, but I have never, ever in my career met another person who has done this) is for typesetting mathematics. The LaTeX macros for math are extremely convenient and the pictorial output from TeX are perfect. This allows you to typeset your mathematics in LaTeX, generate a picture and then paste that picture into an HTML document, or Word document, or whatever. There is one notable file format that is built on top of TeX that also is meant for digital use: Texinfo. This is the original documentation format for GNU. You can write hyperlink documents in Texinfo and it will generate TeX output for high quality print documents, and HTML (as well as a few other formats). It is very limited in its features, though and the HTML output is so-so, IMHO. There are a couple of other document formatting systems that output TeX as well (and in fact, I'm pretty sure there is one that will allow you to build some rudimentary TeX documents with docbook), but I'll let you look for those if you are interested.