A navigation level is a web page that redirects to its first sub page. We show a navigation level at work.
See the site navigation at the left. Beneath the current page, you find the page "I'm a navigation level". Click it and see the result.
The navigation level is added via the sitemap editor. Open the "Add wizard", choose the tab "Function pages" and drag the navigation level to drop it into your sitemap. Sub-pages are added as usual container pages.
In the sitemap editor, the navigation level is highlighted as a blue folder. Below, you see the sitemap for the example presented here.
If you are offline you can open the sitemap editor from this page and reorder the sub-pages of the navigation level. See what happens if you click on the navigation level again. It should redirect to the first sub-page of the navigation, equal which page this is.