The purpose of titles
How can you tell if the person you've just been introduced to is a doctor? The title, "doctor," is the tipoff. Although you may not know immediately what kind of doctor this person is (say, a medical doctor, a dentist, or a PhD, for example), the "doctor" title tells you, at the very least, that this person has earned an advanced degree in something. Likewise, in Great Britain's "peerage system," having a title conveys that one is a "peer of the Royal Realm." From lowest to highest in terms of ranking, here are the titles available:
Here is the difference between a prince and a duke.
Members of the royal family, whether by blood or by marriage, are identifiable by the royal style, "HRH," short for His/Her Royal Highness. Royals are of a higher status than their non-royal peers. This is true even before a royal holds any other titles. For example, HRH Prince Louis ranks higher in the realm than a non-royal duke (most dukes of the realm are, in fact, non-royal).
Who gets to be a royal
The current set of rules assigning royal title and effectively defining who is and isn't a royal, was written in 1917 by King George V (the grandfather of Queen Elizabeth II), according to Marlene Koenig, royal expert, who spoke at length with Reader's Digest about how and why royal titles are conferred. These rules can be modified by the reigning monarch, via legal instruments called "Letters Patent." For example:
Traditional royal titles and what they tell us
Here's what some of the royal titles actually tell us about whatever person who goes by that title:
Official titles of current royal family members
Queen Elizabeth II: Elizabeth Alexandra Mary was the firstborn daughter of the Duke and Duchess of York, later King George VI and Queen Elizabeth (later the Queen Mother). She grew up as "HRH Princess Elizabeth of York." When she married Philip Mountbatten, who had been created as "HRH The Duke of Edinburgh," she also acquired the title, "HRH The Duchess of Edinburgh." Upon her father's death, her title became "Her Majesty, The Queen." Other titles she holds are "Head of the Commonwealth," and "Defender of the Faith." Here is why Her Majesty, The Queen will not be giving up the throne anytime soon.
Prince Philip: Born a prince of Denmark and Greece, Philip Mountbatten renounced his birth-right but was made "HRH The Duke of Edinburgh, Earl of Merioneth, and Baron Greenwich" right before his marriage to Elizabeth in 1947, who was not yet Queen. He was made "Prince Philip" in 1957. Here is why Prince Philip is not "King Philip".
Prince Charles: Charles was born "HRH Prince Charles Philip Arthur George" and later was created "HRH The Prince of Wales, Earl of Chester." The press and the public usually refer to him as "Prince Charles," which isn't his title, but is technically not incorrect either—because blood princes/princesses are styled with their own name alongside the title of prince/princess. Charles is also "HRH The Duke of Cornwall", and when in Scotland, "HRH The Prince Charles, Duke of Rothesay" (this is the one instance when Charles is styled by his Christian name).
Camilla: When Camilla married Charles, she technically became "HRH The Princess of Wales" (although she doesn't use this title) and is also styled as "HRH The Duchess of Cornwall," and when in Scotland, "HRH The Duchess of Rothesay." She is also, technically, "HRH The Princess Charles," but not "Princess Camilla"—because princesses by marriage are styled by their husband's name, as opposed to their own, which is reserved for blood princesses (such as "HRH Princess Eugenie"). That's why even though the press and public have always referred to Diana as "Princess Diana," she was never actually "Princess Diana" but rather "HRH The Princess of Wales," and upon her divorce, "Diana, Princess of Wales." Here are some things you didn't know about Camilla.
Prince William: Born "HRH Prince William Arthur Philip Louis of Wales," he was made "HRH The Duke of Cambridge, Earl of Strathearn, and Baron Carrickfergus" on his marriage to Catherine, and is styled as "HRH The Duke of Cambridge." The press and the public call him "Prince William" for short, which isn't his title, but is technically not incorrect either.
Catherine: When she married William, she technically became "HRH Princess William," but she is styled as "HRH The Duchess of Cambridge, Countess of Strathearn, and Lady Carrickfergus." Although the press and the public often refer to Catherine as variations on "Catherine, Duchess of Cambridge," her first name is not part of her title, and it would only ever become part of her title if she were to become divorced or widowed.
George, Charlotte, and Louis: Thanks to the Queen's Letters Patent of 2012, her great-grandchildren from her grandson, William, were all born "HRH Prince/Princess [first name] of Cambridge."
Prince Harry: Born "HRH Prince Henry Charles Albert David of Wales," he was styled before his marriage as "HRH Prince Henry of Wales" and has always been referred to by the public and the press as "Prince Harry." Upon his marriage, the Queen also made him "HRH The Duke of Sussex, Earl of Dumbarton, and Baron Kilkeel."
Meghan: On her marriage to Harry, she became "HRH The Duchess of Sussex." If Harry had not been granted a dukedom, Meghan would have had the title "HRH Princess Henry of Wales."
Next, find out 50 more things you never knew about the British royal family.