Most of the population of the Tharu tribe are forest dwellers and some practice agriculture. They speak dialects of Tharu which is a language of the Indo-Aryan subgroup. The Terai region is a depositional landform and alluvial plains made by the river Ganga. The other plains are Bhabar, Terai, Bhangar, and Khaddar stretching from North to south. The eastern part of the Tarai region is known as the Duars in Bangladesh .