Benko Gambit Accepted

The move d4 is a common response by white to the black's first move Nf6. By occupying the center, white gains space and restricts black's potential pawn breaks. Additionally, d4 prepares for white's minor pieces to enter the game, gaining control and influence over key squares. This move also allows white to potentially gain a pawn if black accepts the gambit with b5.

Black's move Nf6 aims to control the center and indirectly pressure white's central pawn on d4. This move prepares for the development of the knight to a more active square in the future. Nf6 also opens up lines for the bishop and queen to potentially join the attack on white's center. This move also avoids any potential early surprises or tactics that white may have up their sleeve.

White's move c4 aims to contest and control the center, attacking black's knight on f6 and indirectly supporting white's central pawn on d4. This move also prepares for the development of the knight and the light-squared bishop to their most active squares. c4 also potentially opens up lines for white's queen to join in the attack. By playing c4, white also gains space and restricts black's potential pawn breaks on the queenside.

In the Benko Gambit Accepted, Black's move c5 aims to aggressively contest and control the center, putting pressure on white's pawn on d4. By advancing the c-pawn, Black gains space and activates their pieces, preparing for the development of the knight and the light-squared bishop. This move also potentially opens up lines for the dark-squared bishop to join in the attack. Additionally, playing c5 allows Black to potentially sacrifice a pawn in exchange for gaining an initiative later on.

White's move d5 aims to gain control over the center by occupying the square next to Black's c5-pawn. By advancing the d-pawn, White gains space and restricts Black's potential pawn breaks. This move also indirectly attacks Black's knight on f6, forcing it to move or be exchanged. Additionally, d5 clears the way for the light-squared bishop and queen to potentially enter the game, gaining control and influence over key squares. This move can also lead to a pawn exchange, potentially opening up the position and creating opportunities for both sides.

Black's move b5 puts pressure on White's d5-pawn, attacking it and potentially forcing it to move. By advancing the b-pawn, Black also gains space on the queenside and opens up lines for the queen and bishop to potentially join in the attack. Additionally, b5 prepares for the development of the knight and the dark-squared bishop to potentially active squares. This move can also result in a pawn sacrifice, which Black may be willing to make in exchange for a more active position and potential attacking chances.

In the Benko Gambit Accepted, White's move cxb5 is the key line of this opening and involves accepting Black's gambit pawn sacrifice. By taking the b5-pawn, White gains a material advantage and potentially activates their pieces. This move also opens up the b-file for White's rook to potentially join in the attack. Additionally, cxb5 can potentially create weaknesses on Black's queenside, making it easier for White to mount an attack in the long run. However, accepting the pawn may also mean that White has to deal with Black's active pieces and strong pawn presence on the queenside.

Black's move a6 aims to put pressure on White's recently advanced c4-bishop, potentially forcing it to retreat or exchange. By attacking the bishop with the a-pawn, Black also gains space on the queenside and potentially opens up lines for their pieces. Additionally, a6 prepares for the development of the dark-squared bishop to an active square, such as b7 or a6, where it can help control key central and queenside squares. This move can also potentially offer Black a tactical shot, such as Na6-b4, attacking White's queen and potentially regaining the lost pawn.