Queen's Gambit Declined - Alapin variation
1. d4 d5 2. c4 e6 3. Nc3 b6
White plays the queen's pawn to d4. Black pushes the queen's pawn to d5. White plays the c-pawn to c4.
Black moves the king's pawn to e6. White develops the knight to c3. Black moves the b-pawn to b6.