Heraldry is the art, skills and science that lie behind the state of being a herald. In former times, a herald was not only a privileged messenger, carrying messages between kings and, in time of war, generals of armies; but sometimes a trusted negotiator. He was always responsible for some of the formalities of identification, and the colleges of heralds kept the records of the designs painted on shields, or coats of arms, by which men in armour could be known.
Nowadays, the only active function of heraldry is the maintenance and control of the coats of arms, shields and related badges, mottos, crests and so on that are used officially by many corporations, universities and private people, aristocratic or (officially) 'gentle'. The arcane nature of much of the subtleties of this has given rise to a very specific and technical heraldic language.