@jinmin1988,
This has been covered about a thousand squillion times, all over the web, for a start you can try typing "England Britain difference" into Google -- wait I'll do it for you --
http://www.google.co.uk/search?source=ig&hl=en&rlz=&=&q=england+britain+difference&btnG=Google+Search&meta=lr%3D&aq=f&oq=
but I'm at a loose end so I'll tell you myself.
(1) Political.
There is a nation called "The United Kingdom Of Great Britain and Northern Ireland". This is a political entity, just as the United States Of America, Malaysia, Indonesia, Canada, etc, are. That long name is often shortened to "The United Kingdom" or "The UK". It is made up of three "countries" called England, Wales and Scotland, and a "province" called Northern Ireland.
England, Wales and Scotland are all located on an island near the European mainland called "Great Britain". Northern Ireland is an area of another island nearby called "Ireland".
(2) Geographical.
England is one of the three countries which are located on the island of Great Britain.
So put simply, England is part of Britain. Not the whole, as many people, particularly Americans, seem to think.