Tibet was traditionally divided into three regions, or Chol-kha-gsum (Chol-kha means "region"; gsum means "three"). The Dbus-Gtsang region stretches from Mnga'-ris skor-gsum at the border of Jammu and Kashmir to Sog-la skya-bo near the town of Sog. The Khams, or Mdo-stod, region consists of the territory between Sog-la skya-bo and the upper bend of the Huang Ho (Yellow River), now located in Tsinghai Province. The A-mdo, or Mdo-smad, region reaches from the Huang Ho to Mchod-rten dkar-po in Kansu Province, comprising most of present-day Tsinghai. Tibetans say that the best religion comes from Dbus-Gtsang, the best men from Khams, and the best horses from A-mdo.

Within the three Chol-kha-gsum approximately one-third of the area is uninhabitable, about one-fifth is roamed by nomads, and the rest is occupied by seminomads and agriculturalists, with a small percentage claimed by trappers in the forest belt.

The main agricultural region is the 1,000-mile-long great valley of southern Tibet, stretching from the upper Indus Valley in the west to the valley of the upper Brahmaputra. Most of the agriculture, animal husbandry, and industry of Tibet is concentrated in this valley, which includes the main cities of Lhasa, Jih-k'a-tse, and Chiang-tzu.