For people outside of these zones, they often find it hard to figure out the difference between these two terms.
The United Kingdom is as it says, united, it includes all the countries of the union jack, Wales, Scotland, North & South Ireland and England. The nations of this island share a common passport including Northern Ireland but not the Republic Of Ireland. The Great Britain, is the name given to main island of England that includes Wales and Scotland. Excludes the island of Ireland which is far bigger and separated by a sea. It’s called the great to distinguish it from the French province Little Britain.