What is "drangiana"

Drangiana or Zarangiana (, Drangianē; also attested in Old Western Iranian as Zranka was a historical region and administrative division of the Achaemenid Empire. This region comprises territory around Hamun Lake, wetlands in endorheic Sistan Basin on the Irano- Afghan- Pakistan border, and its primary watershed Helmand river in what is nowadays southwestern region of Afghanistan and the Chagai region of western Pakistan.