Changes

* Save time: Chess programs could use [[Search|search]] from the beginning and look through all possible continuations in detail to find the best next move, but as this is quite time-consuming and there already exists a lot of [https://en.wikipedia.org/wiki/Chess_opening_book_%28literature%29 literature] about different opening linesIn contrast, opening books can play opening moves almost instantly without searching nor heavy computing and help to save time.* Provide a higher quality of play: Searching only even with large depths can't see deep tactics, strategy, compensation, . It may lose temporarily material for long term advantage.* Provide variety: as there already exists a lot of [https://en.wikipedia.org/wiki/Chess_opening_book_%28literature%29 literature] about different opening lines. As book moves are usually chosen [[Pseudorandom Number Generator|randomly]], whereas searches are more or less deterministic.