Millions of people around the world can trace their ancestry to the small area off mainland Europe known as Great Britain. What some don't understand, however, is that "British" doesn't just mean "English." Great Britain refers collectively to the regions (not countries) of England, Scotland and Wales. Throw in the province of Northern Ireland (where some refer to themselves as British and others as Irish), and you then have the United Kingdom of Great Britain and Northern Ireland -- UK for short.

If you have ancestors from the Channel Islands or the Isle of Man, these are direct dependencies of the British Crown, but are not technically a part of the United Kingdom. They are largely self-governing, with the British goverment primarily responsible for their defense.

The term British Isles is often used to loosely describe the island of Great Britain along with its associated islands - the Channel Islands and the Isle of Man. Great Britain is the largest island of the British Isles. Northern Ireland and the Irish Republic form the second largest island. To further muddy the waters, the term Britain is often used informally to refer to the United Kingdom.

Related:
European Geography FAQ
Tracing Ancestors in England & Wales
100 Common Scottish Surnames & Their Meanings
Researching Your Irish Roots