What is the difference between England, Great Britain, and United Kingdom

Here's a Venn diagram showing their relationship:



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. Here, the term "constituent country" is not used in the same way that "country" is usually used; England, Scotland, Wales and Northern Ireland are political subdivisions of the UK, and it is the UK which appears in international bodies such as the United Nations and NATO.

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.

England is part of Great Britain which is part of the UK.

The United Kingdom is a sovereign state consisting of four constituent countries. Three of those countries, England, Scotland and Wales are on the island of Great Britain. The fourth one is Northern Ireland on the island of Ireland.

In summary:

England = a constituent country of the UK

Great Britain = the island England is on, along with Scotland and Wales.

United Kingdom = the state they are all part of, along with Northern Ireland.