Acronym for What You See Is What You Get.
The idea of what's showing on the screen is as close to what you see on paper. Microsoft Word is an example of a WYSIWYG editor. Writing things in LaTeX is not.
It works better as an idea than in practice, a lot of the time. Hence variations of the Acronym such as What You See Is What You Might Get and similar ones.
4 pages link to WYSIWYG:
