what is the difference between English and British literature.

Typically, the term English Literature refers to works
written in the English language.  The term British Literature refers to works written by
the people of the all of the United Kingdom of Britain, commonly referred to as the UK. 
The UK consists of Northern Ireland, Scotland, England, and Wales.  While most British
Literature is also written in English, there are some works written in other languages
that are still considered British Literature.  For example, some works written in Latin
or the Scottish Gaelic are still under the umbrella of British Literature.  Often these
terms might be confusing because there is a period in history where the two terms
overlap.  It was a time when English language works were primarily written in what would
become the UK.