A duel is a formal type of combat, as has been practiced since the fifteenth to the twentieth century in Western societies. It can be defined as a consensual fight between two gentlemen, who use deadly weapons in agreement with explicit or implicit rules are respected by the honor of the contenders, accompanied by sponsors, who can in turn fight each other or not.
In general, and especially in recent decades, a duel is considered an illegal act in most countries. The duel was developing by the will of one of the parties -the defiantly to wash an insult to his honor. The overall goal was not to kill the opponent, but to get "satisfaction", for example by restoring one's honor to jeopardize their lives to defend it. Must distinguish duels tests combat, as the former are not used to determine guilt or innocence, nor constituted official procedures.
Duels were generally illegal in hand, even though in most societies where he was usual, counted on social acceptance. Participants in a duel correctly raised generally were not persecuted, and in cases where they were, they are not imprisoned as a result.
It was considered that only knights had an honor to defend, and therefore upper class was the one qualified to do it: if a gentleman was insulted by someone from the lower class, that not challenging him to a duel, but he inflicted any physical punishment or commissioning his servants to do so.