A constitutional monarchy is a form of constitutional government, where a hereditary monarch is the head of state, unlike in an absolute monarchy, wherein the king or the queen is the sole source of political power, as he or she is not legally bound by the constitution. The levels & types of power & authority held by the Monarch vary from case to case, as does the nature & guarantees of the constitution. This is a system of government in which a monarch shares power with a constitutionally organized government, where the monarch may be the de facto head of state or a purely ceremonial leader. The constitution allocates the rest of the government’s power to the legislature & judiciary.The United Kingdom is a constitutional monarchy, where its succession to the British throne is hereditary, but it excludes Roman Catholics. Under the British Constitution, sweeping executive powers, known as the royal prerogative, are nominally vested in the Sovereign. In exercising these powers, however, the Sovereign normally defers to the advice of the Prime Minister or other ministers. This principle, which can be traced back to the Restoration, was most famously articulated by the Victorian writer Walter Bagehot as "the Queen reigns, but she does not rule".

The royal prerogative is a body of customary authority, privilege, & immunity, recognized in common law & , sometimes, in civil law jurisdictions possessing a monarchy, as belonging to the sovereign & which have become widely vested in the government. It is the means by which some of the executive powers of government, possessed by & vested in a monarch with regard to the process of governance of the state, are carried out,

The Privy Council dates back to Norman times & is one of the oldest parts of Government. These days, however, the Privy Council is simply the mechanism through which interdepartmental agreement is reached on those items of Government business which, for historical or other reasons, fall to Ministers as Privy Counsellors rather than as Departmental Ministers. Although members of the Privy Council are appointed for life, only Ministers of the current Government participate in its day-to-day business & they are accountable to Parliament for all matters conducted through the Privy Council. The Ministerial head of the Privy Council Office is the Lord President of the Council. Privy Council business falls into two main categories: Prerogative business – where there is no legislation allocating the responsibility to a particular Minister, the Privy Council provides a mechanism for Ministerial advice to The Queen, since constitutionally The Queen acts only on such advice. Statutory business – where an Act of Parliament has given order making powers to either the The Queen in Council (Orders in Council) or the Privy Council (Orders of Council).

As Head of State, The Queen undertakes constitutional & representational duties which have developed over one thousand years of history. There are inward duties, with The Queen playing a part in State functions in Britain. Parliament must be opened, Orders in Council have to be approved, Acts of Parliament must be signed, & meetings with the Prime Minister must be held. There are also outward duties of State, when The Queen represents Britain to the rest of the world. For example, The Queen receives foreign ambassadors & high commissioners, entertains visiting Heads of State, & makes State visits overseas to other countries, in support of diplomatic and economic relations.

The Supreme Governor of the Church of England is a title held by the British monarch that signifies titular leadership over the Church of England. Although the monarch's authority over the Church of England is largely ceremonial, the position is still very relevant to the church & is mostly observed in a symbolic capacity. The Supreme Governor formally appoints high-ranking members of the church on the advice of the Prime Minister of the United Kingdom, who is in turn advised by church leaders.

Acts of Parliament, also called primary legislation, are statutes passed by a parliament (legislature).

A Commonwealth realm is a sovereign state in which Queen Elizabeth II is the head of state & reigning constitutional monarch. Each realm is independent from the other realms. As of 2018, there are 16 Commonwealth realms: Antigua and Barbuda, Australia, The Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Solomon Islands, Tuvalu, & the United Kingdom. All 16 Commonwealth realms are members of the Commonwealth of Nations, an intergovernmental organisation of 53 member states. Elizabeth II is Head of the Commonwealth, & head of state in 16 of the members. The remaining 37 have individual heads of state.

An heir presumptive or heiress presumptive is the person entitled to inherit a throne, but whose position can be displaced by the birth of an heir apparent, male or female, or of a new heir presumptive with a better claim to the position in question. Depending on the rules of the monarchy the heir presumptive might be the daughter of a monarch (if males take priority over females & the monarch has no sons), or the senior member of a collateral line (if the monarch is childless); the birth of a legitimate child to the monarch will displace the former heir presumptive by a new heir apparent or heir presumptive. It is not assumed that the monarch & his or her consort are incapable of having further children; the day before Queen Elizabeth II ascended the throne, her father, George VI, was gravely ill & her mother was in her early 50s, but Elizabeth was still considered the heir presumptive rather than the heir apparent. Heir presumptive, like heir apparent, is not a title or position per se. Rather, it is a general term for a person who holds a certain place in the order of succession. The Heir Presumptive now no longer applies to the British line of succession due to the Succession to the Crown Act 2013, which was passed mainly "to make succession to the Crown not depend on gender" & "to make provision about Royal Marriages" (according to its long title), thereby implementing the Perth Agreement in the UK & in those realms that, by their laws, have as their monarch automatically whoever is monarch of the UK. Other realms passed their own legislation.

An heir apparent is a person who is first in a line of succession & cannot be displaced from inheriting by the birth of another person. An heir presumptive, by contrast, is someone who is first in line to inherit a title but who can be displaced by the birth of a more eligible heir.

The Perth Agreement is an agreement that was made by the prime ministers of the 16 Commonwealth realms during the biennial Commonwealth Heads of Government Meeting in October 2011 in Perth, Australia, concerning amendments to the royal succession laws, namely, replacing male-preference primogeniture, under which male descendants take precedence over females in the line of succession, with absolute primogeniture; ending the disqualification of those married to Roman Catholics; & limiting the number of individuals in line to the throne requiring permission from the sovereign to marry. However, the ban on Catholics & other non-Protestants becoming sovereign & the requirement for the sovereign to be in communion with the Church of England remained as the sovereign is the Head of the Church of England. The effects are not likely to be felt for many years; the first two heirs at the time of the agreement (Charles, Prince of Wales, and his son Prince William, Duke of Cambridge) were already eldest born children, & in 2013, William's first-born son Prince George of Cambridge became the next apparent successor.

For men this is a neck bow (from the head only) whilst women do a small curtsy. Other people prefer simply to shake hands in the usual way. On presentation to The Queen, the correct formal address is 'Your Majesty' & subsequently 'Ma'am,' pronounced with a short 'a,' as in 'jam'. For male members of the Royal Family the same rules apply, with the title used in the first instance being 'Your Royal Highness' and subsequently 'Sir'. For other female members of the Royal Family the first address is conventionally 'Your Royal Highness' and subsequently 'Ma'am'.

Royal family curtsy protocol dictates you acknowledge the important people in the room in a specific order that. The queen is the most important royal, so you curtsy to her first. Then, you'd curtsy to the next highest-ranking royal most likely her children in order from oldest to youngest. "Blood princesses," or those females who are born into the royal family, like Princess Beatrice, Princess Eugenie, and Princess Charlotte — are considered to be a higher rank than someone who marries into the royal family. This is because of a rule change Queen Elizabeth enacted in 2005 after Prince Charles married Camilla Parker Bowles. The queen's daughter, Princess Anne, and cousin, Princess Alexandra, no longer have to curtsy to Camilla when she is not accompanied by Charles, as they outrank her as "blood princesses." If Camilla and Charles are together, Anne and Alexandra have to curtsy to her because Charles is of a higher rank than them. A wife takes on her husband's rank when the couple is together. In a sense, the husband's presence validates the wife's royal status. For example, if Meghan Markle and Prince Harry were in a room with the queen, Prince Charles, Camilla, Princess Anne, Princess Beatrice, and Princess Eugenie, Meghan would only need to curtsy to the queen, Prince Charles, and Camilla, because they are the only royals in the room who rank higher than her. In this example, Anne, Beatrice, and Eugenie would actually have to curtsy to Meghan because she takes on Harry's rank, which is above that of those three women. Now imagine that same scenario, except Prince Harry isn't there to accompany his wife. In that case, Meghan would have to curtsy to everyone in the room.