Trooping the Colour is a ceremony performed by regiment

Regiment

A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

s of the British

British Army

The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...

 and the Commonwealth armies

Commonwealth of Nations

The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...

. It has been a tradition of British infantry

Infantry

Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

 regiments since the 17th century, although the roots go back much earlier. On battlefields, a regiment's colours

Colours, standards and guidons

In military organizations, the practice of carrying colours, standards or Guidons, both to act as a rallying point for troops and to mark the location of the commander, is thought to have originated in Ancient Egypt some 5,000 years ago...

, or flags, were used as rallying points. Consequently, regiments would have their ensign

Ensign (rank)

Ensign is a junior rank of a commissioned officer in the armed forces of some countries, normally in the infantry or navy. As the junior officer in an infantry regiment was traditionally the carrier of the ensign flag, the rank itself acquired the name....

s slowly march with their colours between the soldiers' ranks to enable soldiers to recognise their regiments' colours.

Since 1748 Trooping the Colour has also marked the official birthday of the British Sovereign

Queen's Official Birthday

The Queen's Official Birthday is the selected day on which the birthday of the monarch of Commonwealth realms is officially celebrated in Commonwealth countries and in Fiji, which is now a republic. It is an invention of the early 20th century...

.