Queen's Gambit Declined: Structure and Plans

Explanation

In the Queen's Gambit Declined, Black answers the with ...e6. That pawn protects Black's pawn on d5, so Black declines the immediate opportunity to capture on c4 and keeps a firm central presence.

... supports and changes the bishops' development

... preserves the -pawn and refuses the immediate capture on . The advance and support form one central decision.

Black chooses to support the center

Instead of capturing on , ... reinforces and determines which bishop can develop easily.

... preserves the -pawn and refuses the immediate capture on . The advance and support form one central decision.
By clearing , the pawn lets the -bishop develop and helps Black prepare castling.
The same placement on cuts off the -bishop's natural diagonal. Central solidity costs that piece some space.

The choice has a clear benefit and a clear cost. The e6-pawn lets the f8-bishop move and helps Black prepare castling, but it temporarily blocks the bishop on c8. White usually increases pressure on d5 with knights and bishops, and may eventually exchange pawns there. Black develops while preparing ...c5 or ...e5. A pawn break is an advance or capture that challenges an opposing pawn chain and opens lines.

Pressure on calls for a freeing break

The -pawn and -knight converge on . They share a marker because they express one accumulated pressure.

Both sides concentrate resources in the center

White increases pressure on ; Black supports it while preparing a way to challenge .

The -pawn and -knight converge on . They share a marker because they express one accumulated pressure.
The -pawn and -knight support together. They are two defenders of the same point.
The -bishop remains shut in by even after Black has completed kingside development.
... is a break against that can activate the queenside and reduce White's space advantage.
... is a different central break. It requires its own preparation and is not grouped with the ... alternative.

Common confusions

Declined does not mean no later capture

Black refuses the immediate capture on c4, but may take that pawn later when the position makes the exchange useful.

Sources

1.Queen's Gambit Declined - Chess Openings, Chess.com
2.Queen's Gambit Declined, Wikipedia contributors
3.Queen's Gambit Declined, Lichess