Generally speaking: Great Britain = England, Scotland and Wales. UK = the United Kingdom of Great Britain and Northern Ireland, ie. England, Scotland, Wales and Northern Ireland. The Republic of Ireland (often shortened to Ireland) or Eire is not part of either. Just to confuse things, when the UK takes part in something like the Olympics they compete under the name "Great Britain" or "Team GB", but in the Six Nations Rugby competition there's a team called "Ireland" which includes players from Northern Ireland and the Republic of Ireland. To make things even more complicated, later this year Scotland will be taking a vote on whether to become independent. What you can be sure of is that all the countries are part of the British Isles - hope that helps .