According to the official website for the British monarchy, the Order of the Garter is:
…the senior and oldest British Order of Chivalry, founded by Edward III in 1348. The Order, consisting of the King and twenty-five knights, honours those who have held public office, who have contributed in a particular way to national life or who have served the Sovereign personally.
The patron saint of the Order is St George (patron saint of soldiers and of England) and the spiritual home of the Order is St George’s Chapel, Windsor.
Every knight is required to display a banner of his arms in the Chapel, together with a helmet, crest and sword and an enameled stallplate.
These ‘achievements’ are taken down on the knight’s death and the insignia are returned to the Sovereign. The stallplates remain as a memorial and these now form one of the finest collections of heraldry in the world.
The insignia of the Order have developed over the centuries, starting with a garter and badge depicting St George and the Dragon. A collar was added in the sixteenth century, and the star and broad riband in the seventeenth century.
New appointments to the Order of the Garter are usually announced on St. George’s Day (23 April) but the chivalric and installation ceremonies take place in June, on the Monday of Royal Ascot week, known as Garter Day. If there are new Companions of the Order of the Garter, The Queen formally invests them with the insignia at a Chapter of the Order in the Throne Room of Windsor Castle.
Afterwards The Queen and The Duke of Edinburgh entertain the members and officers of the Order at a lunch in the Waterloo Chamber. After lunch the Knights process on foot to a service in St. George’s Chapel, wearing their blue velvet robes, known as mantels, and black velvet hats with white plumes.
The processional route is through the Upper, Middle and Lower Wards of the castle to St. George’s Chapel. The colorful procession is led by the Constable and Governor of Windsor Castle and the Military Knights of Windsor.
On reaching the chapel there is a short service, at the beginning of which the new Companions (if any) are installed. On emerging from the Great West Door of the Chapel, the Sovereign and the other members of the Order return in carriages and cars to the Upper Ward of the castle.
The Queen attends the service along with other members of the Royal Family in the Order…