The Indo-Nepalese group comprises people who speak Sanskrit-derived languages and are strict adherents to Hinduism. Nepali, the official language, is derived from Sanskrit. Differences within the Indo-Nepalese group are marked more by caste (a system of social hierarchy) than by ethnicity. The Tibeto-Nepalese group comprises several different ethnic groups including Newar, Bhutia, Sherpa, Gurung, Magar, Tamang, Rai, and Limbu people. Although most of the Tibeto-Nepalese speak Nepali, each ethnic group also has its own language. While the majority of Nepali people practice Hinduism, the official religion, a strong shamanist element remains in the religious practices of many Tibeto-Nepalese ethnic groups (see Shaman). Buddhism is also important within the country. Buddha, the founder of Buddhism, was born in Lumbini, in present-day Nepal. There is also a small Muslim population mainly located in the Tarai.