http://en.wikipedia.org/wiki/Nepali_language

Nepali is an Indo-Aryan language spoken in Nepal, Bhutan, and some parts of India and Myanmar (Burma).

It is the lingua-franca of Nepal and also one of 23 Official languages of India incorporated in 8th annex of the Indian Constitution. It is a lingua-franca of the state of Sikkim and has official language status in West Bengal's Darjeeling district. Similarly it is spoken in State of Uttaranchal as well as in the state of Assam. Roughly half of the population of Nepal speaks Nepali as a mother tongue. Beside this some casr and religions use their own language as their first language. However, the official language of Nepal is Nepali.

Nepali goes by various names. It was also called Gorkhali or Gurkhali, "the language of the Gurkhas," and Parbatiya, "the language of the mountains." Khaskura is the oldest term, literally speech of the Khas, who were peasants in the Karnali-Bheri basin of far western Nepal since prehistoric or early historic times. Khaskura exists in opposition to Khamkura, a group of Tibeto-Burman dialects spoken by Kham peoples in the highlands separating the Karnali-Bheri basin from the Gandaki basin in central Nepal.