Queen's Gambit Declined - exchange variation
1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. cxd5
White plays the queen's pawn to d4. Black plays the queen's pawn to d5. White plays the c-pawn to c4.
Black advances the king's pawn to e6. White develops the knight to c3. Black develops the knight to f6.
White captures on d5 with the c-pawn.