With old-school text processors (such as Groff and TeX), you can ignore document appearance while writing. Plain-text macros tell post-processors how to lay out a document for printing after writing is done. With word processors (such as OpenOffice Word and StarOffice), you mark up text and see the basic layout of the document as you write.
Some attributes of the traditional Linux publishing tools make them particularly well-suited for certain types of document publishing. Groff and LaTeX (which is based on TeX) come with Red Hat Linux and have been popular among technical people. Reasons for that include:
You can manipulate files in plain text. Using tools such as sed and grep, you can scan and change one document or hundreds with a single command or script.
Scientific notation is supported. With geqn, you can create complex equations. LaTeX and TeX are suited for technical notation. Some math publications require LaTeX.
Editing can be faster because traditional Linux documents are created with a text editor. You usually get better performance out of a text editor than a word processor.
Simple page layouts work well with Linux documentation tools. For example, a technical book with a few flow charts and images can be easily produced and maintained using Groff or TeX documentation tools. Letters and memos are also easy to do with these tools. And, of course, Linux man pages are created with text-based tools.
Also, Linux likes PostScript. Although people think of PostScript as a printing language, it is really more of a programming language (you could write PostScript code directly). Most Linux document-processing software includes print drivers for PostScript. Also, some documents on the Web are distributed in PostScript (.ps).
The drawback to the traditional Linux document tools is that they are not intuitive. Although there are some easier front-ends to LaTeX (see the description of LyX later on), if you are creating documents in a text editor, you need to learn what macros to type into your documents and which formatting and print commands to use.
For many years, the UNIX system documentation distributed by AT&T was created in troff/nroff formats, which predate Groff. The documents used separate macro packages for man pages and guide material. Using a source code control system (SCCS), thousands of pages of documentation could be ported to different UNIX systems. Today, Red Hat still includes the same tools to work with man pages.