Quick summary.
The United Kingdom (UK) is a country that consists of England, Scotland, Wales, and Northern Ireland.
The name Great Britain refers to the island on which most of the non-sovereign countries of England, Scotland, and Wales are situated.
The United Kingdom of Great Britain and Northern Ireland (UK) is an island country that sits north-west of mainland Europe.
It is made up of mainland Great Britain (England, Wales and Scotland) and the northern part of the island of Ireland (Northern Ireland).
It has numerous smaller islands.
London is the capital city of England and the United Kingdom.
It is the most populous city in the United Kingdom, with a metropolitan area of over 13 million inhabitants.