Tibetans are traditionally divided into groups according to geographic origin, occupation, and social status. The plateau was divided into five general regions, each with a distinctive climate: the northern plain, which is almost uninhabited; the southern belt on the Tsangpo River, which is the heart of the agricultural settlements; western Tibet, a mountainous and arid area; the southeast, which has rich temperate and subtropical forests and more rainfall; and the northeast terrain of rolling grasslands dotted with mountains, famous for its herding. Traditionally, settlement patterns were determined by region and by the three major occupations: peasant farming, nomadic herding, and monkhood. Peasants lived in single dwellings as well as village clusters, whereas nomads lived in tents, camping both individually and in clusters as they followed their herds through seasonal migration patterns. Monks lived in monasteries of varying sizes, some reportedly with as many as 10,000 individuals. There are only three major urban centers, all located in the southern belt of the plateau. The nonnomadic society was also divided into hierarchic social groups ranging from the ruler and the noble elite to private landowners, peasants, and craftspersons.
Since the incorporation of Tibet into the PRC after 1950, many Han Chinese have migrated onto the plateau, primarily to the urban centers, where they now outnumber the ethnic Tibetans. Nomads were originally settled into camps but have recently been allowed to resume transhumance patterns.