Short answer
Hijab usually means a headscarf that covers the hair and neck. Niqab is a face veil that leaves the eyes open, and burqa is a full-body covering with a mesh over the eyes, worn mainly in Afghanistan and parts of Pakistan.
The fuller answer
In Arabic, hijab means a cover or a screen, and it is used for a woman's modest dress in general. Scholars agree that Muslim women should cover everything except the face and hands, and they differ on whether the face should also be covered. Most hold that it is not required, and some hold it is recommended or required.
A woman who wears niqab is also making a choice of faith. Other terms include the chador, an outer cloak worn in Iran, and the shayla and al-amira, common in the Gulf. Which of these is worn depends mainly on a woman's culture and conviction.
This answer follows the mainstream Sunni understanding and is general learning, not a fatwa. Where Muslims differ, the answer says so. Have a question of your own? Write to us.