Royals Everything to Know About the Union Jack, United Kingdom's National Flag From the significance of its design to the meaning behind its name, here's what to know about the 400-year-old flag By Skyler Caruso Skyler Caruso Skyler Caruso is a Writer and Reporter of PEOPLE Digital Entertainment. She joined PEOPLE in 2021, but has eight years of experience working in digital publishing with a focus on entertainment and pop culture news. People Editorial Guidelines Published on September 19, 2022 01:38PM EDT Photo: Joe Maher/Getty The Union Jack, also known as the Union Flag, is the national flag of the United Kingdom of Great Britain and Northern Ireland, the Crown Dependencies and the Overseas Territories, and is rooted in a 400-year history. It is largely associated with ideals of pride and patriotism, which is why the flag has been proudly scattered and sported among the tens of thousands of spectators who have lined the streets to celebrate Queen Elizabeth II's long life and reign following her death. While the Royal Standard flag was draped over Her Majesty's coffin during the funeral and several processions, it differs from the Union Jack in that it represents the Sovereign and the United Kingdom. Moving Images from Queen Elizabeth II's Historic Funeral Both flags were notably used to signify the Queen's presence in Buckingham Palace. The Royal Standard would only fly when she was there, while the Union Jack would fly when she was not. In the wake of the Queen's death, the Union Jack is to be flown at half-mast. (The Royal Standard is never flown at half-mast — "even after the death of a monarch, as there is always a Sovereign on the throne.") From the Union Jack's origin to the meaning behind its multiple crosses, here's everything to know about the United Kingdom's national flag. Which countries does the Union Jack flag represent? Hollie Adams/Bloomberg via Getty The Union Jack flag is the national flag of the United Kingdom. It represents the four countries that are united under one Sovereign, including England, Wales, Scotland and Ireland — though since 1921, only northern Ireland has remained a part of the United Kingdom. In addition, commonwealth countries have incorporated the Union Jack within their flags to signify the history of British settlement, including Australia, New Zealand, and Tuvalu. Furthermore, the U.S. state of Hawaii, several Australian states (New South Wales, Queensland, South Australia, Tasmania, Victoria, and Western Australia), and three Canadian provinces (British Columbia, Manitoba, and Ontario) feature Union Jack on their flags. Previously Unseen Photo of Queen Elizabeth Released Ahead of Her Funeral Why is the United Kingdom's national flag called Union Jack? Ed Ram/Getty There is much debate about the exact origin of the Union Jack flag's name. In the 16th century, it was initially called the British flag and in 1625, the word "Union" was introduced. When the flag was first created in 1606, it was ordered primarily to fly at sea, situated atop the main masthead of all English and Scottish ships, warships and merchant ships. Before the 1600s, the term "jack" was used to describe a small flag flown at the bow of a ship. Some believe the "Union Jack" title dates back to Queen Anne's reign from 1702 to 1714, per the royal family's official website. Others believe it derives from the "jack-et" of the English or Scottish soldiers, or from the name of James I who formed the first union in 1603. Another alternative is that the name is rooted in a proclamation by Charles II, "that the Union Flag should be flown only by ships of the Royal Navy as a jack," the royal family website also notes. See the Incredibly Moving Photos of the Queen's 8 Grandchildren Standing Vigil at Her Coffin What do the colors and crosses on the Union Jack flag represent? Zac Goodwin - WPA Pool/Getty The Union Jack consists of three heraldic crosses combined: Saint George's Cross of England, Saint Andrew's Cross of Scotland and Saint Patrick's Cross of Ireland. The layout of the flag has evolved since the first Union Flag — which is what it was initially known as — was created in 1606. The first Union Flag only consisted of England's red cross of Saint George on a white background combined with Scotland's white diagonal cross on a blue background. But since it is not considered permissible to have red on a blue background, according to heraldry, the red cross had to be bordered with white. It wasn't until Ireland became a part of the United Kingdom in 1801 that Saint Patrick's Cross was added to the flag, represented by the diagonal red cross on a white background. Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more! When is the Union Jack flag flown? Dan Kitwood/Getty Initially, the Union Flag was recognized as a Royal Flag. When its present design was deemed official in 1801, it was ordered to be flown solely on all the King's forts and castles. Prior to the Queen's death, the Union Jack was flown above Buckingham Palace, Windsor Castle and Sandringham when she was not in residence. Following her death, it is flown at half-mast. "The Royal Standard is never flown at half-mast, as the Sovereign never dies (the new monarch immediately succeeds his or her predecessor)," the royal family's official website states. Government buildings must fly the Union Jack flag on Royal Family birthdays, Commonwealth Day, Coronation Day, The Queen's official birthday, Remembrance Day and on the days of the State Opening and prorogation of Parliament. In more recent years, U.K. government buildings have been encouraged to fly the flag all year round. In the wake of the Queen's death, the Union Jack flag — in addition to all official flags — should be lowered to half-masted until 8 a.m. on the day after the Queen's state funeral.