What is foreshadowing, and what is being foreshadowed in the story "A Sound of Thunder," by Ray Bradbury?

Foreshadowing is a literary term used extensively by writers that introduces verbal and/or dramatic hints about what will occur later in the story. In science fiction master Ray Bradbury's "A Sound of Thunder," a group of hunters travel back in the past to kill a Tyrannosaurus Rex--the greatest of all dinosaurs. The hunters must follow certain rules and restrictions--specifically, they must not stray from the designated path and kill indiscriminately, for the most simple act can cause a change in the flow of history. However, one of the hunters does just that, and when the men return to the present, they notice changes in people, language and even architectural design. Most noticeably, the recent presidential election results have been reversed. Nearly all of these changes and their possible repercussions, were foreshadowed earlier in the story.