Heraldry is often thought of as the system of graphical identification of the noble class, by way of designs painted on shields, but heraldry involves much more than that. The first medieval identifying images were the seals used by monarchs, churches, cities, and other such institutions to make an impression in wax. These were in use before the 10th century and came into widespread use by the noble class by the 12th century. It was around the 12th century that the use of such identifying marks on military shields came into use, and in many cases, these may have been influenced by the images found on seals already in use.

Early heralds had ceremonial duties, and they began also recording the armorial markings in use during tournaments and battles. Due to widespread conflict of different members of the nobility using the same heraldic charges, heralds soon began to also act as officers of arms, assigning new arms to avoid conflict and hearing cases of existing conflicts, to ensure unambiguous assignment and use of armorial bearings. In post-medieval times, the term heraldry also includes all these duties, as well as all the armorial bearings to which they pertain.

A coat of arms is the complete and distinct design of a shield (or sometimes an oval or lozenge) used for heraldic purposes. This is often surmounted by a helmet, often with a torse and mantle. Supporters (or sometimes a single supporter), as well as a compartment, motto and chapeau. crown or coronet of rank, may or may not also be included. A crest is often used, and in German and Nordic countries, the helmet and crest are considered inseperable from the shield, though in England, particularly during the 19th century, crests became separated from the shield and were often used in letterheads without any shield at all, giving rise to the erroneous notion of a "family crest", which in turn engendered the misuse of the term "crest" to refer to coat armory.