Originally posted by vishyanand
Whats the point of Ba6,Qa4 and Bb7?
Ba6 obviously attacks c4, and more generally Black wants to exert pressure on the a6/f1 diagonal given that the White bishop is going to g2 and not longer contesting the a6/f1 diagonal.
With Qa4, White defends c4 but also hampers the development of Black's knight on b8 since it is now solely responsible for defending the bishop on a6.
Bb7 eases the knight's development once again and now contests the a8/h1 diagonal instead. Of course, White will contest this too with Bg2.
Compare Black playing Bb7 immediately, instead of Ba6. This is also quite common. The difference being that White's queen remains on d1 rather than a4, and that is an important difference: maybe White's queen is better on d1 than a4. Don't assume that a move like Qa4 is necesarily a good development move; the queen may prove to be misplaced on a4. Of course, with GMs willing to play both sides, it's an idea worthy of contesting.
The Queen's Indian Defence (and other openings for that matter) has other moves, the aim of which is to distract the opponent's pieces onto poorer squares. e.g. Black playing a Bb4+, White responding Bd2, and only then Black playing Be7. Again, the idea being that White's bishop is less ideal on d2 (sometimes it goes onto the a1/h8 diagonal via b2, while leaving c3 for the knight - not so easy from d2).