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...Bg7/7. Bc4

7.Bc4
This move places the bishop on a good, active post. However, the drawback is that Nf3 will become unplayable, since Bg4! will put unbearable pressure on d4. It's either Be2/Nf3, Bc4/Ne2 or Bc4/Nf3/h3. In this setup, the bishop will be more active, while in the other setup, the knight will be so. That other setup has increasingly popular since the 1980's.