Queen's Gambit Accepted - 4.e3
1. d4 d5 2. c4 dxc4 3. Nf3 Nf6 4. e3
White pushes the queen's pawn to d4. Black moves the queen's pawn to d5. White pushes the c-pawn to c4.
Black captures on c4 with the queen's pawn. White develops the knight to f3. Black develops the knight to f6.
White pushes the king's pawn to e3.