A chador is a long, cape-like garment that covers the hair and body of some devout Muslim women. It's especially common in Iran for women to wear a chador when they're out in public.
There is a wide variety of head coverings worn by Muslim women in various countries and traditions, including the hijab, khimar, and burka. The chador is mainly native to Iran, where it was primarily worn at funerals before the Islamic Revolution of 1979. Now it's uncommon for an Iranian woman to be seen without a chador, which extends from the head to the ankles. The Persian root is chadar, "scarf or veil," and also "tent or table cloth."