[jules]

Lyx is a WYSIWYG editor for Latex. It shows you quick typesetting in the WYSIWYG editor, but you can compile the underlying Latex document for beautiful typesetting.

[wodenokoto]

No, Lyx is not WYSIWYG, but WYSIWYM. E.g, it doesn't show you how your document will look, but it shows you how it is structured.