When you think of the science fiction genre, you're likely to imagine space battles and aliens, but the genre is broad enough to encompass stories that have nothing to do with extraterrestrials or space travel. Science fiction need only have an element fantasy - that's the fiction part - and the fantasymust be approached in a way that's rooted in rationality or technology, as opposed to magic - that's the science part.
Science fiction movies can be straight-up adventure, like Star Wars or Star Trek, or they can be sophisticated, tech-heavy but earth-bound stories like The Matrix or Inception. They can take place in the future, on another planet or on the other side of the universe, or they can happen right here, right now, in a present that is close to reality, but not quite. They can even be set in the past, as in modern takes on classic Jules Verne stories.
Science fiction movies, especially that contemporary ones with giant budgets and non-stop special effects, tend to be heavy on action sequences, but they don't have to be. They can be gentle, feel-good stories like E.T., or they can be creepy horror movies in sci-fi setting, like Alien.