What does the "central idea" mean in literature?

In literature, the "central idea" is a another way of saying "theme." A theme is the focus, the lesson or the moral learned in a given piece of literature.  If you want to compare it to  Disney Land, the central idea or theme is that of cartoon characters...however, the central theme of a story is like that of The Three Little Pigs; never build your house out of straw, be sure it has a solid foundation.