The Bingo Book is a book that contains any and all information on every missing-nin, which all jōnin and members of ANBU of the major shinobi villages are given by their respective Kage to hunt down and assassinate. The purpose of this is so that the village's secrets and/or kekkei genkai aren't stolen or examined by the enemy. Kirigakure has a special unit within their ANBU called hunter-nin, whose sole purpose is the complete eradication of these missing-nin.
