Foreshadowing is the use of hints or clues to suggest what will happen later in literature.
Example:
John McCall has some good work on this topic at
http://www.benandverse.com/writings/shadowingthereader.htm from his main page
Here is a sample:
Foreshadowing, here, just means hinting at things to come. It’s well known that beginners tend
to be scared of their own foreshadows. And the truth is they are sometimes right. If, by
foreshadowing, you mean that the narrator or someone summarizes what will happen—especially,
just before it happens—then suspense gets punctured. Or, rather the reader, who loves grade A
suspense—"what’s going to happen?"—will have to settle for grade B suspense—"how will it
happen?"