1…c5 shows White that Black would like to play the Sicilian Defense. Note that Black uses a flank pawn to fight for control of the central square d4.
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White now has many reasonable moves to consider. We would like to examine the Open Sicilian in this challenge.

2.Nf3 develops a piece and fights for control over d4 and e5. This move also prepares to open the center.

2…d6 is one of the three most common moves at this juncture. Black also frequently chooses to play 2…e6 and 2…Nc6, while 2…g6, 2…Nf6 and 2…a6 are less popular.
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Again White has many different plans to choose from. In this challenge we are looking for the most direct way of opening up the center.

3.d4 is the most popular move in this position. White wants to open up the position immediately.

Black happily complies with 3…cxd4. From a strictly positional point of view, this pawn exchange favors Black as he exchanges a Black flank pawn for one of White’s center pawns.
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Both sides are trying to develop more pieces.

4.Nxd4 recaptures the pawn and centralizes the knight. In the Open Sicilian White tries to generate active piece play in order to compensate for Black’s more solid pawn structure.

4…Nf6 develops a knight towards the center while also eyeing the e4-pawn.
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Both sides are trying to develop more pieces.

5.Nc3 protects the e4-pawn, develops a piece and also eyes the d5-square.

5…a6 leads to the Najdorf Defense. Other common choices  are 5…Nc6, 5…g6 and 5…e6. The pawn on a6 takes away the b5-square from White’s knights and the f1-bishop and it also gives Black the option to advance the b-pawn to b5.
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White can choose from many systems against the Najdorf. Some of them aim directly at Black’s king, while others take a more positional approach.

6.Be2 is one of the many fine moves in this position. By placing this bishop on e2, White usually prepares kingside castling.

6…e5 is in the spirit of the Najdorf defense. Black could have played 6…e6, but that would likely transpose to a Scheveningen Defense. Note that in the Najdorf Black usually only plays …e5 after …a6 has already been played.
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Black’s last pawn move is gaining time while claiming some space in the center.

7.Nb3 is the most popular choice. On b3 the knight will take part in White’s queenside plans later in the game and does not get in the way of any other pieces. 7.Nf3 is also playable, while 7.Nf5? d5 undermines White’s center.

7…Be6 tries to plug the whole on d5 with another piece. When Black pushed the e-pawn to e5, he had to be well aware of the fact that White will have a grip on the d5-square for a long time.
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Both sides are eager to complete developing their pieces. The side that will complete this task first usually has more options to choose from.

8.0-0 moves the king into safety and connects the rook with White’s other pieces.

8…Be7 develops a new piece and gives Black the option to castle kingside next.
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White would like to attain a space advantage on both sides of the board.

9.Be3 places the bishop on the best square in this system. However, sometimes White leaves the bishop on c1 for a little longer if the idea is play f2-f4 soon and then recapture on f4 without having moved this bishop yet. Look to stop Black’s queenside plans first. However we prefer a plan for gaining space on the queenside first.

9.a4 prevents Black from gaining space on the queenside with …b5. White may also want to push the a-pawn to a5 later on so that White’s pieces could use the b6-square as an outpost. Usually Black would next castle kingside with 9…0-0 to get the king into safety and connect the h8-rook with the rest of Black’s army. Then White has two main plans to choose from. The first one is to play mostly on the queenside with moves such as a4-a5, f2-f3, Bc1-e3, Qd1-d2 and then moving the rooks to c1 and d1 and the c3-knight to the stronghold on d5. 
White’s other plan consists of pushing the f-pawn to f4 and trying to establish a superiority in the center. Black will have to finish development himself while trying to find some active play. Black will typically seek counter play along the half-open c-file and try to play the freeing …d6-d5 or …b7-b5. You may wonder what would happen if Black played 9…d5 immediately? In that case, White could obtain a slightly better endgame after the series of exchanges 10.exd5 Nxd5 11.Nxd5 Qxd5 12.Qxd5 Bxd5 13.Be3 with the plan of playing 14.Rfd1 and 15.Nc5. This line requires a great deal of patience for the Black player as White has some space advantage and more options to choose from. 

We hope that you have become familiar with a few basic ideas that face both sides in the Open Sicilian. Many of these patterns recur in other challenges and thus allow you to get used to them over time.