Smileless2012
I've just googled this and a hijab is traditionally a garment that covers the upper body including the face.
These days the niqab and burka are normally treated as being different from the hijab. The first covers the head and chest but allows the eyes to be seen, the second is all enveloping covering the woman entirely.
The hijab ( in its various forms of Shayla, Hijab Amira, Chador, Khimar and Hijab) is just a headscarf of various dimensions worn to cover the hair but expose the face, much the same as the Queen often wears.