Which countries make up Britain?

Great Britain is comprised of England, Scotland and Wales.

If Northern Ireland is added, the country then gets its full name of The United Kingdom of Great Britain and Northern Ireland.

What we normally think of as Britain consists of the UK, the Channel islands and the Isle of Man.
Great Britain is the largest of the 2 main islands of the British Isles, the other being the Republic of Ireland.

Great Britain is made up of the countries of England, Scotland and Wales.

In 1927 the province of Northern Ireland was incorporated, along with Great Britain, into the new Sovereign State of the United Kingdom of Great Britain and Northern Ireland. Now referred to normally as "the UK"