Science fiction is a term that lays claim to a huge
expanse of
territory, although some of it is quite thinly
settled.
Several years ago Damon Knight, a very well known author and editor, was talking about definitions of science fiction on the now defunct GENIE SFRT. He had studied what was actually published in science fiction magazines and shelved on the Science Fiction book shelf in bookstores and libraries. The actual material was much broader than any hard and fast definition he had ever heard proposed.
Science fiction includes stories about the future, stories about parallel universes, stories about alternate history, stories about the distant (pre historic) past, stories about aliens, stories about other worlds, and too many other kinds of things to list conpletely, but see the soft links below.
Ar its best, I believe science fiction can be the most thought provoking literature available, forcing us and helping us to think about who and what we are, where we are going, and what we want to become. As with most of what is published today, I believe most of it will be forgotten in fifty years.