This article is from the Amiga FAQ, by Ignaz Kellerer with numerous contributions by others.
A word processor is the typical application for writing notes, letters or reports on a computer. Unless you prepare newsletters on a weekly basis, your word procesor is probably your workhorse program. Thus choosing one you are comfortable with determines how comfortable you are with your computer. Word processors can offer a variety of features, and many can approach the sophistication required for Desktop Publishing (see DTP) but no one uses them for programming, for which text editors are more suited.
One distinguishes between Wysiwyg programs (What you see is what you get) and page layout languages. Wysiwyg programs should be fast, comfortable and easy to use. Most people prefer them. The alternative is an approach that works similar to compilers. You feed text files to a a program that produces the layout which may be previewed on screen or printed. LaTeX takes this approach. See TeX. Lout is another such system which seems smaller, easier to learn and has full documentation included, but it is nonstandard. Lout produces Postscript output. (I don't know if this is an advantage or disadvantage. ;-) See Postscript. Both programs are freely distributable.
There are a lot of wysiwyg programs, but only commercial products: FinalWriter, Final Copy II, Wordworth, Word Perfect, AmiWrite, Beckertext II, Maxon Word and many others. I don't dare to recommend any. All I can say is: Give yourself time to make a selection.