The Dooars or Duars are the foothills of the eastern Himalayas in North-East India around Bhutan. Duar means 'door' and the region forms the gateway to Bhutan from India. There are 18 passages or gateways through which the Bhutanese people can communicate with the people living in the plains. This region is divided by the Sankosh River into the Eastern and the Western Dooars. The Western Dooars is known as the Bengal Dooars and the Eastern Dooars as the Assam Dooars. Dooars is synonymous with the term Terai used in Nepal and northern India and form the only nitrate rich plain in India.