WYSIWYG stands for What You See Is What You Get. A WYSIWIG web page editor is an application where you can build a web page a bit like you would build a page on a word processor or desktop publishing app. You place the various items (i.e. text, links, images) where you want them to appear on the page and the editor generates HTML to represent this. When you view one of these pages on a browser it should look just like it did on the editor.
Well kind of but, the wysiwy(d)g editor I am using now at the precise moment is doing exactly what I want it to do. Although programs like frontpage make a mess of html programs like word do exactly what you want them to do.