Queen placement in the Dragon [FEN &quot;&quot;]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 g6 5.Nc3 Bg7 6.Be3 Nf6 7.f3 O-O 8.Bc4 e6 9.O-O a6

Here is a line from a game of mine. I made the movee 10. Qd3, but my computer program says Qd2 would have been a much better move. Why is that?
One of Black's development plans will include moves like Nd7 intending Ne5 hitting the Q and Bishop if the Q is on d3.
This will cost White an important tempo in this dynamic opening.
Black's plans revolve around control of the c4 square hoping to place a piece on this square. Depending on White's particular move order Black may play b5, Bb7, Nd7, Nb6, Nc4, Rc8.
To counter this Q side action of Black, White needs to get active on the K side: Qd2 allows the B to h6 plan to exchange off the key defensive Black B. In due course after completing development White can plan a pawn storm against the B King.