What is the difference between England, Great Britain, Britain, and the United Kingdom?

An all too common question! The simple answer lies in abstracting progressively larger.

1. England is the part of the island of Britain which excludes both Wales and Scotland.
2. The terms Great Britain and Britain both mean the same thing, namely the entire island joined together by the 3 regions of England, Scotland and Wales as a whole.
3. The term United Kingdom describes the whole island of Great Britain (or Britain if you prefer) as well as North Ireland (not the Republic of Ireland however).

While we are on the subject, it is also important to discuss the term United Kingdom in relation to the term Commonwealth. The two should not be confused with eachother. The Commonwealth is is something altogether different entirely. It describes a free association of nearly 50 independent nations formerly subject to British rule (during the Empire) that maintain friendly and practical links with the UK. Of these, only a handful of the Commonwealth countries such as Australia, New Zealand, Canada, Jamaica, Belize, Barbados, and the Bahamas still officially recognize the Queen as their head of their state and consequently pay taxes to her majesty. See www.thecommonwealth.org