United Kingdom (UK) or Britain- consists of four countries, England, Scotland, Wales and Northern Ireland.  It is a sovereign country in north-western Europe, off the north-­western coast of the European mainland. Northern Ireland shares a land border with the Republic of Ireland. Otherwise, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west. The Irish Sea separates Great Britain and Ireland. 

The United Kingdom is a unitary parliamentary democracy and constitutional monarchy. The monarch, Queen Elizabeth II, has reigned since 1952. The capital and largest city is London, a global city and financial center with an urban area population of 10.3 million. Other than England, the constituent countries have their own devolved governments, each with varying powers.

Resource: https://en.wikipedia.org/wiki/United_Kingdom