What is Opening theory in chess?
The body of analysed and established best-play sequences for the first moves of a game.
Theory covers the most important openings and defences in depth, sometimes 20 or more moves of analysed play. Beginners benefit more from understanding opening principles than memorising large amounts of theory.
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- TranspositionReaching the same position via a different order of moves.
- NoveltyA new, previously unplayed move in a known opening line.
- RepertoireThe set of openings a player has prepared and regularly plays.
- Main lineThe most theoretically important and commonly played continuation in an opening.
- SidelineA less common opening variation that deviates from the most popular main line.
- Development leadHaving more pieces developed (off the back rank) than the opponent.