Britain, transliteration of "Britain", originally means "Britain" because Britain comes from the "British Isles".

English, so, English is an adjective of English, which refers to people, language, English and English.

England, later, because the British Isles are divided into three regions: England, Scotland and Wales, in which England is the capital of imperial power and all the British "British Isles" are ruled by English people, England is used to refer to Britain, which means both Britain and England.

English is an adjective in Britain. Like British, it refers to language, people, Britain and England. ....

There is little difference between Britain and England when they refer to Britain, but they refer to the same meaning, only some idioms are different.