what is the difference between U.K. & Great Britain?

Answer 1

Great Britain, technically, is merely the largest island of the British Isles, comprising England, Scotland, and Wales.

The United Kingdom includes Great Britain, Northern Ireland, as well as Bermuda, Gibraltar, Pitcairn Islands, the British Indian Ocean Territory, Falkland Islands, and British Antarctica (among other territories). It also technically includes the dependencies of the Channel Islands and the Isle of Man.

However, the UK is often referred to as Great Britain or Britain anyway.

Answer 2

they have different names