Queen's Gambit Declined - 4.Bg5 Be7
1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. Bg5 Be7
White advances the queen's pawn to d4. Black advances the queen's pawn to d5. White moves the c-pawn to c4.
Black plays the king's pawn to e6. White develops the knight to c3. Black develops the knight to f6.
White develops the dark-squared bishop to g5. Black develops the dark-squared bishop to e7.