The Most Noble Order of the Garter, founded in 1348, is the highest order of chivalry and the most prestigious honour in England and of the United Kingdom, and is dedicated to the image and arms of St. George as England's patron saint. It is awarded at the Sovereign's pleasure as his personal gift, on recipients from the United Kingdom and the Commonwealth realms. Membership of the order is limited to the Sovereign, the Prince of Wales, and no more than twenty-four members, or Companions. The order also includes supernumerary knights and ladies (e.g., members of the British Royal Family and foreign monarchs).

The order's emblem, depicted on insignia, is a garter with the motto Honi soit qui mal y pense (Middle French: "shame upon him who thinks evil upon it") in gold lettering. Members of the order wear such a garter on ceremonial occasions.

New appointments to the Order of the Garter are always announced on St George's Day, 23 April, as Saint George is the patron saint of England

More information on the Wikipedia page [1]
