There is not really an exact definition to the word "Literature". It has not been one in more than 300 years and it is very unlikely that I can explain what is it. If I try to give an exact definition of what literature is, I would be placing my self above all the great thinkers there have existed.
One of the many definitions I can write about is that literature comes from the word "litera" which means letters. Literature is the art of language and since all of the arts express the beauty we can assume. The world needs literature because man needs beauty in his life.