Sometimes you want a custom URL for your webpage... for example, yoursite.com/home/
1. create page with SEF-URL "home" (the best is page with ID = 1)
2. associate Root namespace to "page"
3. set Frontpage to needed URL. Don't use the Custom page option.
If you select Custom Page option, content of this page will be displayed on main page (like on /index.php)