The Commonwealth dates back to the British Empire where several countries were considered territories under British rule.
As some of these nations gained independence over time, the modern Commonwealth was slowly born in 1949 when it became a voluntary union.
From then on, all nations were considered equal members of the Commonwealth and other countries were also free to join.
The Commonwealth’s purpose, according to the Royal Family’s website, is to “promote international cooperation and commercial links between people around the world”.
These nations together make up 2.5 billion of the world’s population, according to the Commonwealth website.  In addition, 32 of the world’s 42 small nations, which are countries with a population of 1.5 million or less, are in the Commonwealth.
Here’s a look at the 56 nations and additional territories under the monarchy:

NATIONS IN THE KINGDOM

Of the 56 members of the Commonwealth, only 15 are in the realm that regard the King as their head of state.  This includes Antigua and Barbuda, Australia, Bahamas, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines , Solomon Island, Tuvalu and the UK.  which includes England, Northern Ireland, Scotland and Wales.
Officially, there were 18 other nations that held the crown as their head of state throughout history.
This included;  Barbados, Fiji, Gambia, Ghana, Guyana, Ireland, Kenya, Malawi, Malta, Mauritius, Nigeria, Pakistan, Sierra Leone, South Africa, Sri Lanka, Trinidad and Tobago and Uganda.
Most recently, in 2021, Barbados became the first country in three decades to remove the Queen as their head of state, but remain within the Commonwealth as a republic.

DEMOCRATIC NATION WITHIN SOCIETY

The rest of the Commonwealth nations recognize King Charles as head of the union, but do not regard the Crown as their head of state.
Unlike his hereditary role as Crown, a unanimous vote among the group’s leaders in 2018 assigned him that title after the Queen’s death.
Among the Commonwealth of Nations, 36 nations are considered democracies, while five have their own monarch, which includes: Brunei Darussalam, Lesotho, Malaysia, Eswatini (officially Swaziland) and Tonga.

MAP OF PRESENT & FORMER COMMUNITY NATIONS

Map of current, former Commonwealth countries (Jasna Baric / CTV News Graphics) Click here for a larger version of the map

CROWN DEPENDENCIES & BRITISH TERRITORIES

In addition to the nations that have ties to the British monarchy, there are additional places where the crown plays a role.
The Queen held titles to three island territories within the British Isles, which include: the Isle of Man in the Irish Sea and the Channel Islands which include the Bailiwicks of Jersey and Guernsey.  Until the Queen’s death he was titled in the Isle of Man as Lord of Mann and in the Channel Islands he was known as the Duke of Normandy.
Similar to the nations in the realm, 14 other territories have a constitutional link with the United Kingdom and recognize the Crown as their head of state.  These areas are self-governing and have a combined population of 300,000 citizens, according to the Commonwealth Parliamentary Association.  These territories include: Anguilla, Ascension, Bermuda, British Virgin Island, Cayman Island, Falkland Islands, Gibraltar, Montserrat, St.  Helena, Tristan da Cunha, Turks and Caicos Island.  
Jasna Baric map