In the universe of "Planet Ladder", there are at least nine worlds that have been discovered, almost like parallel dimensions.  The more "advanced" worlds use Collapsers to move from world to world.  Collapsers create a black hole which sucks anyone and anything in the vecinity to another world.(See the author's note in the back on the explination of collapsers, Vol 1.)  Thing is, it's completely random.  This is what I gathered from Bambi's explination of the worlds to Kaguya:

*note that this was writen based on a Japanese translation, this will soon be according to the American rendition

Ancient: This is the first of the civilized worlds.  Though it was the first, it almost doesn't exist.  It was "destroyed" long ago and there is no land.

Eden:  This world use to be the most beautiful of all, but the planet system was destroyed so completely that even the Sun was destroyed.  Kyououji Seeu is supposedly the only person to have survived and still lives there.

Earth: This is our world.  Criminals were sent here long ago and polluted this planet.  Our planet is so plauged by sin that communication is forbidden.  Kaguya grew up here.

Tereney: This is where Kaguya and Gold wind up.  Bambi lives here.  This is a very small empire in the middle of civil war and about to destroy itself.  Bambi says that the rulers are idiots that survive by sucking up people who live on Geo.

(nameless):  This world is a collection of small countries, each thinking seperately, and with their own unique status.  Rumors lead everyone to believe that the Wise Ones, Way of the Comet and Way of the Meteor, are here whispering with one another.

Jius:  A peaceful little planet with a small population.  Jius is under the control of Geo.

Geo:  This planet is the victor in the war between the worlds. The Wise One of the Way of Appetite(don't ask), Didius Dii is living here. The take the teaching of Ancient and make it almost religious, and even forecast the end of the Worlds.  They are also looking for the Princess. Kura has controlled the empire for over 300 years, he is the master of Niyuxlight.

Asraitsu: This planet believes in the Sun. The master of Zenith Light, Idou, lives here, even though currently he obeys Geo's orders.

(nameless):  A world that had few people, and was almost destroyed in the war.