The United Kingdom of Great Britain and Northern Ireland (which is usually shortened to just the UK or United Kingdom) is a political union made of up of four countries, England, Scotland, Wales and Northern Ireland. England, Scotland and Wales share the island of Great Britain, which lies just off the northwest coast of continental Europe. The fourth country, Northern Ireland, is a portion of another island, which is split between Northern Ireland and the Republic of Ireland, an independent country, in the south. The UK also has overseas territories such as Bermuda and Gibraltar.
The union of Great Britain and Northern Island is the latest that has occurred over the last 300 years. Originally Scotland and England were two entirely separate countries with their own monarchs and political systems, and Wales fell under the control of England and was known as a principality.