Opening

Main article: Chess opening
A chess opening is the group of initial moves of a game (the "opening moves"). Recognized sequences of opening moves are referred to as openings and have been given names such as the Ruy Lopez or Sicilian Defence. They are catalogued in reference works such as the Encyclopaedia of Chess Openings. There are dozens of different openings, varying widely in character from quiet positional play (for example, the Réti Opening) to very aggressive (the Latvian Gambit). In some opening lines, the exact sequence considered best for both sides has been worked out to more than 30 moves. Professional players spend years studying openings and continue doing so throughout their careers, as opening theory continues to evolve.
The fundamental strategic aims of most openings are similar.

Development: This is the technique of placing the pieces (particularly bishops and knights) on useful squares where they will have an optimal impact on the game.
Control of the center: Control of the central squares allows pieces to be moved to any part of the board relatively easily, and can also have a cramping effect on the opponent.
King safety: It is critical to keep the king safe from dangerous possibilities. A correctly timed castling can often enhance this.
Pawn structure: Players strive to avoid the creation of pawn weaknesses such as isolated, doubled, or backward pawns, and pawn islands – and to force such weaknesses in the opponent's position.

Most players and theoreticians consider that White, by virtue of the first move, begins the game with a small advantage. This initially gives White the initiative. Black usually strives to neutralize White's advantage and achieve equality, or to develop dynamic counterplay in an unbalanced position.


 The set of openings a player has specialized in is called an opening repertoire. The main elements a player needs to consider in a repertoire are:
As White, whether to open with 1.e4, 1.d4, 1.c4, or 1.Nf3
As Black, a defense against any of these openings
A very narrow repertoire allows for deeper specialization but also makes a player less flexible to vary against different opponents. In addition, opponents may find it easier to prepare against a player with a narrow repertoire.
The main openings in a repertoire are usually reasonably sound, that is, they should lead to playable positions even against optimal counterplay. Unsound gambits are sometimes used as surprise weapons, but are unreliable for a stable repertoire. Repertoires often change as a player develops, and a player's advancement may be stifled if the opening repertoire does not evolve. Some openings which are effective against amateur players are less effective at the master level. For example Black obtains active play in return for a pawn in the Benko Gambit, amateur players may have trouble defending against Black's activity while masters are more skilled at defending and making use of the extra pawn. Some openings which are played between grandmasters are so complex and theoretical that amateur players will have trouble understanding them. An example is the Perenyi Attack of the Sicilian Defense (see diagram) which yields an immensely complicated and tactical position that even strong players have difficulty handling, and that is beyond the comprehension of most amateurs