tibet
A region under the control of China since Kublia Khan claimed it under the Yuan Dynasty.  When the Ming dynasty defeated the Mongols, they inhereted the territory and communication continued throughout the Ming dynasty.  During the Qing Dynasty, China sent residential commissioners called amban to Lhasa and these amban are equal rank to the Dalai Lama.  After the fall of the Qing, china became a republic under the nationalist government and Britain, Tibet and China decide what to do with Tibet.  Britain recognized Tibet as under chinese Suzerainty just like Russia recogzized Mongolia.  Similiar to Mongolia, the British drew up an agreement where Tibet will be seperated into outer Tibet (modern day Tibet) ruled by the Dalai Lama and inner tibet (parts of present day sichuan and qinghai) where the religous aspect will be ruled by the Dalai Lama.  Unlike Mongolia with the russians, the nationalist party never signed the agreement.  Tibet as well as other provinces enjoyed de facto independence when the Chinese nation was torn by warlordism, Japanese invasion, and civil war (1911-1949).  However the nationalist still maintain sovereignty over Tibet.  Through the Succession of states theory in international law (Yuan, Ming, Qing, ROC, PRC)Tibet is still part of China and is now legally a province of China just like Xin Jiang and Inner mongolia.  Tibet is also known as Xizang to the chinese meaning western treasure.   
Tibet (Xizang)is a province in the west of China.   