The Catalan is a very important opening in modern chess. White offfer a pawn sacrifice on c4 and develops his light-squared bishop to g2. In many variations it is precisely this bishop which exerts enormous pressure down the h1-a8 diagonal. The 14th world champion in the history of chess, Vladimir Kramnik, enriched this opening with numerous ideas and took it out of its sleeping beauty status.
Open Variation: 1.d4 d5 c4 e6 3.g3 Nf6 4.Nf3 dxc4
In the Open Variation Black takes the pawn on c4 and hopes by doing so to gain time for counterplay. In many variations he even tries to defend the pawn for a long time. White can recover the pawn at once with 5.Qa4+, but usually the first player continues with the development of his kingside and hopes for nice compensation, especially thanks to his strong bishop on g2.
Closed Variation: 1. d4 d5 2.c4 e6 3.g3 Nf6 4.Nf3 Be7
In the Closed Variation Black at first does without the capture on c4 and first develops his kingside. A typical variation goes: 5. Bf1-g2 0-0 6. 0-0 dxc4 Only after both sides have brought their kings to safety does Black take on c4 7. Qd1-c2 a7-a6 White mainly recovers his pawn with the queen and Black plans to attack the queen with …b7-b5. White can now take the pawn on c4 or prevent Black’s …b7-b5 thrust with 8. a2-a4. In this case Black should develop his light-squared bishop via d7 to c6.