Modern English with analytic grammar has developed from Anglo-Saxon an important event that influenced the language was the Battle of Hastings in 1066. Here William Conqueror defeated the original inhabitants. Then many Normen came to England that are French origin (castle, garage, fashion, prince). But English has borrowed words from many other languages too e.g. Spanish, Latin. It is obvious that other languages are influenced by the English vocabulary.
There are 5 main types of English that differ in pronunciation, spelling and vocabulary but the differences are not so crucial that they could avoid understanding. They are: British English, American English, Australian English, Indian English and African English.

Great Britain is the official name for the Union of England, Scotland and Wales. The name used for Britain and Northen Ireland is a United Kingdom. The United Kingdom together with Canada, Australia, New Zealand and some other territories is called the British Commonwealth of Nations. The majority of inhabitants of Great Britain speak English. But only the English, it means the inhabitants of England, are of Germanic origin while the Welsh and Scots are of Celtic origin. In spide of these differences in the origin of British nations, most inhabitants, especially those living outside UK, say they are British.