Kingdoms
There are four kingdoms in which Human and Faunus live. These small pockets are the few places that Humans have managed to protect from the Grimm, allowing technological growth and general shelter. These four kingdoms are known as Atlas, Mistral, Vacuo, and Vale. The kingdoms seem to be at peace with one another.
Each kingdom has a governing council to represent it and it's people's needs. Some people try to leave the walls and set up villages on occasion, however they tend to vanish quickly when they can no longer hold off the Grimm.
Defense
Each kingdom also has a military similar to the ones in our own world, however Remnant's military technology is definitely more advanced than our own. They're more uniform than the huntsmen, working fast and in swarms to effectively deal with Grimm.
Huntsmen are heavily trained individuals who choose to fight to defend the kingdom individually instead of with the military. Huntsmen have their own guide that you can read to learn more.