Shows a list of your categories, with links to each category listing. It will display up to two levels of category.
This takes each of your top-level categories and displays them as individual items on the main menu. This is useful when you only have a couple of categories and not much else on the main menu.
Will add a link titled "All Categories" to the end of the list of categories. The link takes the user to a single page displaying a complete list of categories. This is useful when you have a large number of catgories.