The Neo-Terran Caste System is how the NTIH manages new frontiers and colonies. It was invented and enforced by Drusus V. It gave the Neo-Terran government full control of the alien species that were enslaved.
These planets are where most slaves of the hegemony live. Urban worlds are where workers are born and raised. When another planet needs more workers or a colony needs to be established, the government pulls family units at random to fill the demand. Urban worlds can have up to one trillion inhabitants, and the minimum population of a planet to be considered an urban world is 15 billion.
These planets are used for all sorts of things, most of which involve large scale production of Battleships and other large warships.
Neo-Terrans living on Urban worlds find themselves with a lot of time on their hands, as all of their needs are fulfilled by the Hegemony's extensive territories. So the average citizen spends their time perusing more intellectual careers.
These planets are where everything from pans to battleships are produced. Moderately populated and closely governed, these worlds are designed to be as efficient at production as possible. On each one, millions of slaves toil.
While most food in the universe is grown on O'Neill Cylinders, some exotic foods need very precise conditions that are very expensive to emulate using an O'Neill Cylinder. Many worlds have food production facilities on them used for these crops. Unlike most worlds, these worlds are completely automated.