Burqa, Hijab, Niqab, ... they are NOT the same ...

So, is there is a difference? Yes.  Yes :)

Hijab: it can be conceptualized as a head scarf.

A couple of years ago, we had a visitor from Bahrain as a house-guest for ten days or so.  She always wore a hijab.  And, it turned out that it was her choice to wear a hijab--even her mother does not wear one.
But, this was in Bahrain, which is one of the less restrictive Persian Gulf societies.

Now, let us suppose we expand the covering to most of the body--except the face.  In other words, anybody can see the entire face of the woman, despite that all-covering garment.  Well, that is the chador.

As a kid growing up in India, I think I have seen many women in chadors.  But then in India, I recall that everything was given a common word of purdah.  Purdah itself, according to Wikipedia, has Persian/Urdu origins.  But, the purdah that we generically referred to in India is more like the Niqab or burqa.

With the niqab, well, one can at least see the eyes and eyebrows.  This is also what a German reporter wore for a day to get an idea of how others might respond to a woman wearing a niqab. 
With the burqa, there is a small veil/slit for the eyes.  This is one serious covering up.
(Source for the images used here.)

As a kid, I did not see very many women in India in a burqa.  Even now, when I visit, maybe I see a lot more of the chador and niqab, but not many burqa-clad women.

Here is one of my favorite Hindi songs where you ... well, watch it :) Click here for an English translation of the lyrics