Queen's Gambit Declined Slav - exchange variation
1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. cxd5 cxd5
White moves the queen's pawn to d4. Black moves the queen's pawn to d5. White pushes the c-pawn to c4.
Black plays the c-pawn to c6. White develops the knight to f3. Black develops the knight to f6.
White captures on d5 with the c-pawn. Black captures on d5 with the c-pawn.