People debate about the definition of the fantasy genre and what it means. There are some that say all fiction is fantasy since fiction books are not true stories. Others say Fantasy is any book that deals with things that are not real, but this definition is too broad and ends up with the inclusion of science fiction, horror and any book that has strange occurences. In my years of experience in reading in the genre and about it, I have found a definition that I think explains it best.Fantasy is a literary genre that deals with nonrational phenomena. It inclues works in which events occur, or strange places or creatures that could not occur or exist according to rational or scientific explanations. The nonrational phenomena don't fall within human experience or behave by natural laws as we know them. Fantasy is about the human spirit in its spiritual reality and leads to joy. It provides growth by experience. It is different from other genres like science fiction:
"Fantasy differs from science fiction in two important ways. First, in science fiction the writer at least pretends that the unusual events are part of the physical universe, bound by scientific laws. The wonder in science fiction is rational, not supernatural. Fantasy is not rational. It makes use of a specified supernatural element, or else just the irrationality of dream. Second, fantasy has a very different pedigree. Fantasy is as old as literature" (Darrell Schwietzer)
The genre has six characteristics (some of these traits can be found in other genres too). First, there is a story with a beginning, middle and end. The fantasy has common characters and heroism. There is an evocaton of another world usually. Fantasy employs magic and the supernatural. Most books involve a struggle between good and evil. Lastly, there is usually a quest involved in the story.
Confusion about the definition of fantasy will continue. The one I use is the easiest to understand. I hope that it is helpful to you.