Queen's Gambit Accepted - Ericson variation
1. d4 d5 2. c4 dxc4 3. Nf3 b5
White pushes the queen's pawn to d4. Black pushes the queen's pawn to d5. White plays the c-pawn to c4.
Black captures on c4 with the queen's pawn. White develops the knight to f3. Black plays the b-pawn to b5.