Chess Opening Theory/1. d4/1...Nf6/2. c4/2...g6/3. Nc3/3...d5/4. cxd5/4...Nxd5/5. e4/5...Nxc3/6. bxc3/6...Bg7

6...Bg7
With this move, Black occupies the long diagonal with his bishop and prepares the vital break ...c5.