Black has to capture with the pawn and accept an isolated queen pawn, which is actually not bad in this position.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g2g3  3... d7d5  4. f1g2  4... f8b4 [%c_arrow b1c3;keyPressed;none;from;b1;opacity;0.8;to;c3;persistent;false,c1d2;keyPressed;none;from;c1;opacity;0.8;to;d2;persistent;false,b1d2;keyPressed;none;from;b1;opacity;0.8;to;d2;persistent;false] A very popular choice in this particular move order of the Catalan Opening. This check forces White to transpose the game to a Nimzo-Indian after 5.Nc3, place the bishop in a slightly worse position with 5.Bd2, or place the knight in an undesirable square after 5.Nd2. 5. b1d2  5... e8g8  6. g1f3  6... b7b6  7. e1g1  7... c8b7  8. b2b3 A simple and logical move, preparing to develop the bishop. 8... b8d7  9. c1b2  9... d8e7  10. a2a3  10... b4d6  11. f3h4 [%c_effect h4;square;h4;type;Interesting;persistent;true][%c_arrow h4f5;keyPressed;none;from;h4;opacity;0.8;to;f5;persistent;false] An interesting move that shows a small problem with putting the queen on e7. White wants to capture the pawn on d5 and then place the knight on f5. 11... g7g6 [%c_arrow g6f5;keyPressed;none;from;g6;opacity;0.8;to;f5;persistent;false] Useful to protect the f5-square, although it weakens the kingside a little bit. 12. b3b4 A new move. 12... c7c5 This is forced, otherwise White just plays c4-c5. 13. b4c5  13... b6c5  14. c4d5 