Cadency labels of the British royal family

Heraldic labels are used to differentiate the personal coats of arms of members of the royal family of the United Kingdom from that of the monarch and from each other. In the Gallo-British heraldic tradition, cadency marks have been available to "difference" the arms of a son from those of his father, and the arms of brothers from each other, and traditionally this was often done when it was considered important for each man to have a distinctive individual coat of arms and/or to differentiate the arms of the head of a house from junior members of the family.

Source: Wikipedia — Cadency labels of the British royal family (CC BY-SA 4.0)