In computing, WYSIWYG (/ˈwɪziwɪɡ/ WIZ-ee-wig), an acronym for What You See Is What You Get,[1] refers to software which allows content to be edited in a form that resembles its appearance when printed or displayed as a finished product,[2] such as a printed document, web page, or slide presentation. … In general, WYSIWYG implies the ability to directly manipulate the layout of a document without having to type or remember names of layout commands.[4]
History
Before the adoption of WYSIWYG techniques, … Users were required to enter special non-printing control codes (now referred to as markup code tags) to indicate that some text should be in boldface, italics, or a different typeface or size.
https://en.wikipedia.org/wiki/WYSIWYG