WYSIWYG stands for "What You See Is What You Get," and is pronounced "wihzeewig." WYSIWYG refers to software that accurately represents the final output during the development phase. For example, a desktop publishing program such as Photoshop is a WYSIWYG graphics program because it can display images on the screen the same way they will look when printed on paper. Word processing programs like Microsoft Word and Apple Pages are both WYSIWYG editors, because they include page layout modes that accurately display what the documents will look when printed.
While WYSIWYG originally referred to programs that produce physical output, the term is now also used to describe applications that produce software output. For example, most Web development programs are called WYSIWYG editors since they show what Web pages will look like as the developer is creating them. This means that the developer can move text and images around the page to make it appear exactly how he or she wants before publishing the page on the Web.
When the page is published, it should appear nearly the same on the Web as the way it looked in the Web development program. Of course, as most Web developers know, there is no guarantee that a Web page will look the same in two different browsers, such as Internet Explorer and Firefox. But at least a WYSIWYG editor can give developers a close approximation of what the published page will look like.