The capitol is the richest, biggest part of Panem. The capitol receives the goods from all of the twelve districts. Only people born with a lot of money can afford to live in the capitol. The people here are used to their every need being catered to.
As you can see, the environment, however harsh or nourishing, affects the attitude and appearance of the characters.
District twelve is the poorest district. Their industrial trade, coal, is the least popular and all of their profit goes to the capitol. They are strictly governed. This district is crime-ridden and unsafe. Most of the citizens die of starvation or sickness.