The litter box is hidden inside a cabinet that seals the odor and provide some privacy to the kitties while doing their business. The idea of separating compartment and mesh is to scrape litter off the cat's claw before they exit the litter box. And the vertical ones works the same way as the horizontal ones except the kitty have to go "downstairs" instead of just to the adjacent room.
Cat litter box
Little kitten hiding inside a shoe
magicalnaturetour: Flower hat by Stephan Brauchli