Genres

Here is a list of some genres. It is in no way a complete list, since there are a ton of sub-genres and genres that might exist but haven't garnered a noticeable following yet.

Realistic Fiction—
Examples in Literature: An Abundance of Katherines by John Green, To Kill a Mockingbird by Harper Lee, and Counting by Sevens by Holly Goldberg Sloan.
Examples in Films: Dog Days, Forrest Gump.

Realistic Fiction is fiction that is meant to mimic reality, meaning that it follows the same physics and "rules" of real life. Characters are meant to be realistic and the events of the story are meant to be possible in real life. Realistic fiction can be a great way to show real life problems and faults of society.

Historical Fiction—
Examples in Literature : The Scarlet Letter by Nathaniel Hawthorne, Bud, not Buddy by Christopher Paul Curtis, and Gone With the Wind by Margaret Mitchell.
Examples in Films: Phoenix, Braveheart, Apocolypto.

Like Realistic Fiction, Historical Fiction is meant to mirror reality, except the reality of the past. This means that the author does a lot of research to insure the book is historically accurate. It can be used to remind us of the hardships of the past or shows us how we have not rid our societies of certain problems that were prominent in the past.

Science Fiction—
Examples in Literature : Fahrenheit 451 by Ray Bradbury, Ender's Game by Orson Scott Card, The Time Machine by H.G. Wells, and The Lunar Chronicles by Marissa Meyer.
Examples in Film: Limitless, Star Trek, Doctor Who.

Science Fiction is speculative fiction that explores the possibilities of science, other planets and dimensions, undiscovered creatures outside of this world (or in it), and utopian, dystopian, or post-apocalyptic societies. It may include elements of fantasy (like Star Wars or Doctor Who), or it omits these fantastical elements and the world of the story includes only what is considered to be scientifically possible.

Fantasy—
Examples in Literature: The Harry Potter series by J.K. Rowling, The Hobbit by J.R.R. Tolkien, The Chronicles Of Narnia by C.S. Lewis.
Examples in Films: Inception, Shrek, Wizard of Oz, The Quest for Camelot.

Fiction deals with the fantastical— dragons, fairies, elves, vampires, you name it. These worlds are not meant to mimic reality, as they include magic and strange rules (or lack thereof) of physics). The settings of these fantasy worlds are pretty versatile, since they can be a completely different world of tucked away in the earth or hidden in plain sight.