English literature is a loose term which can have a variety of meanings. As normally used, it refers to the literature written by inhabitants of the British Isles in English or Scots, but not in any form of Gaelic. There may be variations on this usage.
Depending on how it is used, it may or may not include literature written in Old English. It will almost certainly include literature written in Middle English, in order that Chaucer can find a place.
After Chaucer, Elizabethan literature is normally considered to be the first great flowering. The term "Elizabethan" is often extended into the reign of James (though, particularly with drama, the term "Jacobean" is sometimes used). Following on, various terms are sometimes applied, such as "Restoration", "Augustan", "Romantic", "Victorian and "Edwardian".