A chess opening is the group of initial moves of a chess game. Recognized sequences of opening moves are referred to as openings as initiated by White or defenses, as created in reply by Black. There are many dozens of different openings, and hundreds of named variants. The Oxford Companion to Chess lists 1,327 named openings and variants. These vary widely in character from quiet positional play (e.g. the Réti Opening and some lines of the Queen’s Gambit Declined) to wild tactical play (e.g. the Latvian Gambit and Two Knights Defense, particularly the Traxler Variation). In addition to referring to specific move sequences, the opening is the first phase of a chess game, the other phases being the middlegame and the endgame.

Aims of the opening
Closed games
Flank openings
Indian systems
Nomenclature
Open games
Semi-open games
Unusual first moves
Other black responses