Is Great Britain the same as the UK?
No, Great Britain and the United Kingdom refer to different areas.
Great Britain is very often, but incorrectly, used as a synonym for the sovereign state properly known as the
United Kingdom of Great Britain and Northern Ireland or the
UK for short.
If you look at the full name of the UK, you will see that the UK includes Great Britain
AND Northern Ireland.

Great Britain
United Kingdom
Great Britain is a political term which describes the combination of
England,
Scotland, and
Wales, the three nations which together include all the land on the island. It is also a geographical term referring to the island on which the greater parts of England, Wales and Scotland are situated.