1 WYSIWYM vs WYSIWYG
WYSIWYM stands for What You See is What You Mean; WYSIWYG stands for What You See is What You Get;
Microsoft -- Word is always considered as a example of WYSIWYG. Today I have a look at the tool named LyX, which is an example of WYSIWYM. From an end user's point of view, there are more similarity than difference between them.
They both display the the resulted layout on the fly; they both provide button to typeset the document.
The difference I can see between then is -- LyX use text file, while Word use binary file. But I don't think it matters.
In my humble opinion, the real difference between Word and LyX/LaTeX is as the following. In Word, you typeset in the lower level, you can control all the details but it also need more effort. In LyX/LaTex, you typeset in higher level, you only need to figure out the logic structure of the document. The resulted layout is not decided by you, you actually just share the layout developed by the expert. I think it is the key advantage of WYSIWYM.