Gruenfeld - exchange variation
1. d4 Nf6 2. c4 g6 3. Nc3 d5 4. cxd5 Nxd5
White plays the queen's pawn to d4. Black develops the knight to f6. White plays the c-pawn to c4.
Black pushes the g-pawn to g6. White develops the knight to c3. Black plays the queen's pawn to d5.
White captures on d5 with the c-pawn. Black captures with the knight on d5.