The real Queen's Gambit

 

The Queen's Gambit is the chess opening that starts with the moves:

1. d4 d5

2. c4

It is one of the oldest opening and is still commonly played today. It is traditionally described as a gambit because White appears to sacrifice the c-pawn; however, this could be considered a misnomer as Black cannot retain the pawn without incurring a disadvantage. Also, this kind of opening is one of the oldest known in chess. It was mentioned in the Göttingen manuscript of 1490 and was later analyzed by Gioachino Greco in the 17th century. In the 18th century, it was recommended by Philipp Stamma and is sometimes known as the "Aleppo Gambit" on his honor. During the early period of modern chess, queen pawn openings were not in fashion, and the Queen's Gambit did not become commonplace until the 1873 tournament in Vienna. 

As Wilhelm Steinitz and Siegbert Tarrasch developed chess theory and increased the appreciation of positional play, the Queen's Gambit grew more popular, reaching its zenith in the 1920s and 1930s, and it was played in all but 2 of 34 games in the 1927 World Championship match between José Raúl Capablanca and Alexander Alekhine. After the resumption of international chess activity following World War II, it was less frequently seen, as many players moved away from summetrical openings, tending to use Indian Defences to combat queen  pawn openings; however, it is still frequently played. 

With 2. c4, White threatens to exchange a wing pawn (the c-pawn) for a center pawn (Black's d-pawn) in order to dominate the center with e2-e4. Note that Black cannot hold the pawn, for example: 1.d4 d5 2. c4 3. e3 b5? (Black tries to guard their pawn but should pursue development with 3...Nf6 or 3...e5) 4. a4 c6? 5. axb5 cxb5?? 6. Qf3! winning a piece. The Queen's Gambit is divided into two major categories based on Black's response: the Queen's Gambit Accepted (QGA) and Queen's Gambit Declined (QGD). In the QGA, Black plays 2...dxc4, temporarily giving up the center to obtain freer development. In the QGD, Black usually plays to hold d5. Frequently Black will be cramped, but Black aims to exchange pieces and use pawn breaks at c5 and e5 to free Black's game.

Technically, any Black response other than 2...dxc4 (or another line with an early ...dxc4 that transposes into the QGA) is a Queen's Gambit Declined, but the Slav, Albin countergambit, and Chigorin Defense are generally treated separately. There are so many QGD lines after 2...e6 that many of them are distinctive enough to warrant separate treatment. The Orthodox Defense and the Tarrasche Defense are two important examples. (See Queen's Gambit Declined for more).

After 1. d4 d5 2. c4:

2...e6 (Queen's Gambit Declined or QGD). This is the main line, with many variations.

2...dxc4 (Queen's Gambit Accepted or QGA). Less popular than the QGD, it nevertheless has a solid reputation. 

2...c6 (Slav Defense). This is a solid response, although many variations are very tactical. 

2...e5 (Albin Countergambit). A sharp attempt by Black to gain the initiative. 

2...Nc6 (Chigorin Defense). It takes the game away from the normal positional channels of the QGD and has been favored by Alexamder Morozevich at the top level; it appears to be playable for Black. 

2...Bf51!? (Baltic Defense). It is an offbeat but playable line.

2...c5 (Symmetrical Defense). This is rarely played; although it has not been definitely refuted, the play seems to favor White. 

2...Nf6?! (Marshall Defense). It named after Frankk Marshall, who first devised the move, he briefly played it in the 1920s before abandoning it. 

2...g6?! (Alekhine idea). White can gain the advantage by 3. cxd5 Qxd5 (3...Nf6 4. Qa4 +/-) 4. Nc3 Qa5 5. Nf3 Bg7 6. Bd2 c6 7. e4 Qb6 8. Bc4! Bxd4 9. Nxd4 Qxd4 10. Qb3 Qg7 11. 0-0 +/- (Minev).