What is the attire that a woman is permitted to wear in front of other women and her mahrams, and what is the ruling on the niqab – is it obligatory?

It is permissible for a Muslim woman to wear what covers from the navel to the knee in front of Muslim women, and to cover her entire body except for the face, hands, and feet in front of non-Muslim women. As for her mahrams and sons who are close to puberty, she wears what covers her entire body except for the head, arms, and feet. A woman must cover her face and hands in front of non-mahram men.