 Black's typically develops his queen with Qc7, and he has a choice of whether or not to push the c-pawn to c4.The benefit of pushing the c-pawn is that should white capture play dxe6 and after the recapture fxe6 attack the e-pawn with either Ng5 or Nd4, black has the opportunity to defend the pawn with Nc5.Alternatively black can refrain from pushing the c-pawn to c4, which prevents white from using the d4-square for his knight in some variations.