The first moves of a chess game are called the "opening". A chess opening is a name given to a series of opening moves. Recognized patterns of opening moves are "openings" and have been given names such as the Ruy Lopez or Sicilian defence. They are listed in reference works such as the "Encyclopaedia of Chess Openings". There are dozens of different openings. They range from gambits, where a pawn, say, is offered for fast development (e.g. the King's Gambit), to slower openings which lead to a maneuvering type of game (e.g. the Réti opening). In some opening lines, the sequence thought best for both sides has been worked out to 20–30 moves, but most players avoid such lines. Expert players study openings throughout their chess career, as opening theory keeps on developing.