The United Kingdom is a country that includes England, Scotland, Wales, and Northern Ireland. Its official name is “United Kingdom of Great Britain and Northern Ireland.” England, Wales, Scotland, and Northern Ireland are often mistaken as names of countries, but they are only a part of the United Kingdom.
The British Isles is another term altogether and encompasses Great Britain, the island of Ireland, and several other smaller islands, such as the Isle of Man. The Isle of Man is not a part of the United Kingdom or the European Union, even though its Lord is the Monarch of the United Kingdom.
The Commonwealth of Nations is a voluntary association of countries that were formerly British colonies. Members of the Commonwealth of Nations recognize the United Kingdom Monarch as their own king or queen, but remain politically independent.