Borderland
Most of the borderlands of the Realms are similar in their social structure. It is the place where tribes (like the Northern tribes) of "barbarians" roam the landscape, living off the lands and either protecting the local Freemen or attempting to raid their settlements.
Landscapes
The landscapes of the borderlands are generally devoid of most human touch with large areas of just pure wilderness. Spread out are singular trading posts, small fortified villages and hermits as well as the semi-permanent settlements of the local tribes. The only permanent structures of the tribesmen are various shrines and holy sites that are abandoned for the greater portion of the year.
Generally, the hills, woods or even mountainous areas of the borderlands are harsh and requires people who matches the same description.
Socioeconomy
There is roughly a single person per square mile across the borderlands, with greater or less populations from area to area. About half the people living in these "uncivilized" areas are Freemen, who either made themselves thus or were "granted land" here by some noble house leader who considers their family to be in control of the lands. These houses will of course notice that they are mistaken in case they ever bring any sized group of military to the area and they meet the other half of the population.
About half of the population are what people in the Realms call "barbarians". They are people who have learned to live in the tough climate and world of the borderlands where true freedom can be had. They are (mostly) not weighed down by a lot of possessions and many of these tribes are quite mobile. At the very least, they don't put that much effort into the structures they build themselves, and can move if the need arises.
The tribes hail from the same people who walked all of these lands well before the Barbarian Conquest and their ancestors hail to the times when the Nine Kings rose to power and where most 'romantic' ideas of warfare originates among all of the Realms. They still hold to many of these believs and despite what people say have a strong sense of personal honour and what is right and just. This does frequently conflict with other tribes' sens of honour, of course, so conflict frequently ensues between tribes as does intermarriage.
Besides quabbling and trading with each other, the tribes also protect the Freemen; at least the Freemenwho pays them tribute. Paying too little or no tribute can result in a 100% tribute collected by force, further along the line. Freemen have escaped the grasps of gentry only to having to live life outside the edge of civilization. Besides tributing and trading with the tribes they also infrequently trade with civilization for additional supplies that are not provided from the lands.
It is a dangerous choice where you need wits, endurance and charm as well as a strong hand in order to survive. If a competing tribe gets angry they may take it out on the Freemen, so many of them choose to join up in minor, but well fortified, villages so they can withstand a raid until their tributed tribesmen chase off the invadors - or are defeated and the tribite change hands.
Regions
Tribes