No, they're for editing text for content entries (like this one) except that instead of using markup, you use a WYSIWYG editor in the browser. It actually creates marked-up text in a textarea for submission (usually to a database), but there's a live rendered overlay that the user actually works in (rather than having a separate preview area). There are buttons for applying bold, italic and underline effects (and they usually catch common keyboard shortcuts, like Ctrl+I), changing font faces (thankfully, you can opt not to allow font selection), making text larger and smaller, adding subscripts and superscripts, numbered and bullet lists, and so on. And you can usually paste formatted text in from applications like Microsoft Word and maintain formatting. Use cases? Blog entry editing, content creation (with or without approval workflow) -- that sort of thing.
