If you are easily confused about whether you should be saying England, Britain or the United Kingdom then do not fear. There are many people in the same position as you! It is even confusing for people from there! The terms are often used interchangeably but do have different meanings.
Even though it is easy to make a mistake with these different terms, you may accidentally cause offence to someone so here is a small guide to highlight the main differences.
The British Isles is a group of over 6000 islands which lie off the coast of mainland Europe. This includes the countries of England, Scotland, Wales, Northern Ireland and The Republic of Ireland as well as the channel islands (Jersey/Guernsey). All these islands have a total land mass of 315,159 km2 and a population nearing 70,000,000.
The British Isles is made up of thousands of islands but there are 2 which are far larger than the others. The biggest is Great Britain which consists of England (pop.53,000,000), Scotland (5,300,000) and Wales (3,000,000). The second largest island is Ireland which again is split into different parts. The majority of the island of Ireland is taken up by the Republic of Ireland (4,600,000) and in the North East we can find Northern Ireland (1,800,000).
The Republic of Ireland is its own sovereign state. It is a completely different country from the rest of the British Isles. It uses the euro, it has its own Government, laws, customs and language (Irish). However, it is culturally very similar to its closest neighbours.
The United Kingdom is made up of Great Britain (England, Scotland and Wales) and Northern Ireland. The UK is once again a full independent state. The full name is actually "The United Kingdom of Great Britain and Northern Ireland".
The UK is often described as a country of countries. Each individual country has a degree of autonomy and each country has its own Parliament where it can draft some of its own laws. Within the UK in addition to English there are some minority languages such as Welsh, Scottish Gaelic, Irish and Cornish.
Each country of the UK has its own sporting bodies and competes as separate nations in many international events such as football, rugby etc. On the other hand, for the Olympics and the Eurovison Song Contest the UK is represented together. Interestingly, people born in Northern Ireland can choose who they wish to represent between the Republic of Ireland and the UK for events such as the Olympics.
To make matters slightly confusing; people from England, Scotland and Wales are all known as British, but people from Northern Ireland are known as Irish (despite being UK citizens). Whereas, those from the Republic of Ireland are also Irish but this time are Irish citizens.
It would be possible to make the conversation even more confusing if we were to discuss the "British Commonwealth" or British Overseas Territories (Gibraltar, Caymen Islands, Falklands etc) or Crown Dependencies (Isle of Man etc). But we will leave that for another day!