Tibetan is spoken in Tibet, Bhutan, Nepal, and in parts of northern India (including Sikkim). It is classified by linguists as a member of the Tibeto-Burman subgroup of the Sino-Tibetan languages.
Tibetan is written in a very conservative syllabary script based on the writing system of the ancient Sanskrit language of India. Used in its present form since the 9th century, it was developed as a means of translating sacred Buddhist texts that were being brought into Tibet from India. The writing system derived from the pronunciation of the language as it was in about the 7th century, and varies in many ways from colloquial Tibetan as it spoken today.
Source: Dharma Haven