This is a placeholder for how to build wizzy themes.
Name is the predefined name for that class of theme element.
If you want your theme to work with others you HAVE to use these names. So create a directory called whatever your theme is called. The way themes work is that DW looks on a page for any image that has the same class as a class you have defined in your theme. So you could actually put other markup in that themelet tag if you want - like tables or other things like layers. Now make all your images and create a stylesheet for a site.