So I guess a lot of people are in some doubt as to what the difference is between England, Great Britain, the British Isles and the United Kingdom. Here I present a handy-dandy Venn diagram to explain this.

The Republic of Ireland and the United Kingdom are the only two sovereign states in this image. They are shown in red. Ireland and Great Britain are both islands and are shown in green. England, Scotland, Wales and Northern Ireland are constituent countries of the United Kingdom and are shown in orange.

You have the basic idea. There are many other islands in the British Isles which are not shown here. Most of these are politically part of England, Scotland, Wales, Northern Ireland or the Republic of Ireland, with the exceptions of the Isle of Man and the Channel Islands, which are British crown dependencies and not part of the UK (or ROI) at all.

Complications

The UK's full name is "The United Kingdom of Great Britain and Northern Ireland". Citizens of the UK are called "British". One British person is called a Briton.

The ROI's full name is "The Republic of Ireland" (if you are speaking English) or "Éire" (if you are speaking Irish). Citizens of the ROI are called "Irish".

Irish citizens are not British citizens. British citizens are not Irish citizens. God help you if you forget this when you encounter an Irishman.

Ethnically:

• People from England are called English.
• People from Scotland are called Scottish.
• People from Wales are called Welsh.
• People from Northern Ireland are called Northern Irish.
• People from Ireland are called Irish.

There is no such thing as English, Scottish, Welsh or Northern Irish citizenship. English, Scottish, Welsh and Northern Irish people almost always hold British citizenships. Of course, anybody, living anywhere in the British Isles, can have any ethnicity, and hold any citizenship.

Many people living in Northern Ireland (which is part of the UK) are Irish citizens. Some British citizens living in Northern Ireland (which is part of the UK) classify themselves as Irish-ethnic. Some people living in Northern Ireland would even like Northern Ireland itself classified as Irish i.e. made part of the ROI instead of the UK. This is a contentious point.

The ROI is not British. However, the "British Isles" include both the UK and ROI. Irish citizens and Irish-ethnic people hate this, but there is no consensus on what to call it instead. (May I humbly suggest "The British and Irish Isles"?)

England, Wales, Scotland, Northern Ireland and the Republic of Ireland frequently field separate teams in such sports as rugby, football (i.e. the World Cup), cricket and so on. Meanwhile, the Irish international rugby team is comprised of players chosen from both the ROI and Northern Ireland. This is largely because our various nations have been playing rugby, football and cricket for centuries, whereas the current political arrangement of the British Isles was only established in 1920.

Lastly, to be pedantic, this is actually an Euler diagram, not a Venn diagram.