Seppuku is when a samurai committs ritual suicide after dishonoring himself via disemboweling himself with his katana while kneeling and is decapitated by a fellow samurai's katana. Until the Meiji Restoration in the late 1800s seppukku was reserved only for samurai.
Seppuku was a key part of Bushidō, the way of the warrior, in that it either prevented the capture of a samurai or restored his honor. Seppuku was also used as an alternative to normal execution. Those who did not belong to the samurai caste were not expected to commit seppuku. This was because seppuku's purpose was to restore one's honor as a warrior. Samurai needed a superior warrior's permission to commit seppuku.
Sometimes a daimyō was called upon to perform seppuku as a means for peace.
In time, committing seppuku came to involve a detailed ritual. This was usually performed in front of spectators if it was a planned seppuku, not one performed on a battlefield. A samurai was bathed, dressed in white robes, and fed his favorite meal. When he was finished, his instrument was placed on his plate. Dressed ceremonially, with his sword placed in front of him and sometimes seated on special cloths, the warrior would prepare for death by writing a death poem.