The United Kingdom, Great Britain and the British Isles
Many people (and not only visitors from other countries!) are confused by the different terms used to describe the territories of these islands. The explanations below may help to clear up some of the confusion.
Great Britain – this refers to Scotland, England and Wales.
The United Kingdom – this refers to the nations of Great Britain and also Northern Ireland. You may not be aware that there are two separate parts to the island of Ireland. Northern Ireland is part of the UK, while the Republic of Ireland broke away in 1922 and is now an independent and legally separate state. The Republic of Ireland’s geographical territory is mostly in the south part of Ireland, although it also occupies part of the north-west. Confusingly, its correct title is simply "Ireland", but many people call it the Republic of Ireland so that they can differentiate between it and Northern Ireland.
The British Isles – this refers to all the islands, including the Republic of Ireland and the dependencies (these are the tiny islands such as the Isle of Man which have their own little legal systems). However this is just a geographical term, not a legal term. The United Kingdom has no legal powers over the Republic of Ireland.