What is an "opening book"?
An opening book is the equivalent of a human's "game records".
Humans can play by following game records, and software can play by following an opening book. (An engine only calculates and has nothing to do with opening books, although some engines may have a built-in one. Pikafish has no built-in opening book.)
- The main purpose of an opening book is to save time and reduce the chance of losing.
- Some opening books also aim to lure the opponent into complex positions, exploit mistakes in the opponent's opening book, or reach positions where engines tend to go wrong, in order to seek winning chances.
- Although called an opening book, just like game records it can contain any position. Middlegame positions, endgame positions and composed endgames can all be included if you want.
- An opening book is completely independent of the engine, with no cooperation between them. The engine itself does not read opening books.