With around 30 years experience programming, having started in about 1980, I haven't got a clue how to answer that question. So the question being asked is "academic"; the course notes will tell you what it is you need to say to get the marks. If you want an explanation of what the book says then you need to post what the book says and not just the question.
Or you can hope that someone else round here is on the same course as you and recognises the question. This could be unlikely.