Welcome to the crazy world of wazers , I'm sure you'll like it here!
To answer your question about levels: http://giussani.typepad.com/photos/unca ... ection.jpg
ok, that might be a bit extreme but as you can see most roads is at different heights (levels) above the ground. Setting roads to the right levels simply tells Waze that this road is above or beneath the other road and thus it won't complain to you later that you have roads intersecting without a junction!
Re: Levels