Please explain the meaning of this question.

Question

I am reading the AC++. When I have finished the chapter 5, I met a question 5-1.

What I want to ask is not how to work it out, yet is the meaning of this question. I even can't catch what the author want me to do.

Maybe just because I am fresh for coding~

Will you kind enough to explain the question for me?

Thanks for your time~ :)

The question is described like below:

5-1. Design and implement a program to produce a permuted index. A permuted index is one in which each phrase is indexed by every word in the phrase. So, given the following input,

  The quick         brown fox 
jumped over the     fence
The quick brown     fox 
                    jumped over the fence
         jumped     over the fence
            The     quick brown fox 
    jumped over     the fence
                    The quick brown fox

Answer 1

The term permuted index is another name for a KWIC index, referring to the fact that it indexes all cyclic permutations of the headings. Books composed of many short sections with their own descriptive headings, most notably collections of manual pages, often ended with a permuted index section, allowing the reader to easily find a section by any word from its heading. This practice is no longer common.

From: http://en.wikipedia.org/wiki/Key_Word_in_Context

ps: you can access wikipedia via http://www.proxify.com