Queen's Gambit Declined Slav - 4.Nc3
1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3
White pushes the queen's pawn to d4. Black advances the queen's pawn to d5. White plays the c-pawn to c4.
Black advances the c-pawn to c6. White develops the knight to f3. Black develops the knight to f6.
White jumps the knight to c3.