- Speculative Fiction: This is a mother genre. It encompasses all forms of fantasy and science fiction.
- Fantasy: This encompasses all forms and sub-genres of fantasy. The minute you find yourself explaining that something happens because of magic with no further explanation, you need to consider that your story, if nothing else, has fantasy elements. The same can be said if you include elves, dragons, gnomes, or anything else thoroughly fantastic.
- High/Epic Fantasy: This is the most common idea of fantasy out there. It's not set on Earth. It has fantasy creatures and races galore and seems to function on a different level than Earth ever does. The world is completely fabricated by the author (i.e "The Lord of the Rings" Trilogy, "Dungeons and Dragons", "Eragon").
- Urban Fantasy/Contemporary Fantasy: If your fantasy story takes place in a major metropolis (like New York City, Seattle, Los Angeles) on Earth, it's urban fantasy. If it takes place on Earth but not in a major metropolis it's considered contemporary fantasy. The line is often very blurry between these two sub-genres - it depends on who interprets your story's genre.
- Paranormal: Close to fantasy, but not quite. This is a type of speculative fiction dealing with things like ghosts, satanic rituals, Voudou, or anything else that's not a completely foreign concept to Earth (elves=foreign, ghosts=not foreign).
- Science Fantasy: A blending of fantasy elements, like magic, and science-fiction elements. Things like opening a portal to a magical world or summoning a magical being using advanced technology would fall into this genre. The Q, from Star Trek, would also be considered a form of science fantasy.
- Science Fiction: This encomapsses all sub-genres of science fiction. Anything with advancements in technology far beyone our own, alien visitors/wars, or any other form of scientific advancement we can't, as of yet, use or make a prototype of is considered science fiction.
- Hard Science Fiction: Not so much a sub-genre as a classification, hard sci-fi is the type of science fiction that uses only actual science to make everything function without stretching beyond the actual capacity of a theory or technology. There is also a heavy focus on the science in the story.
- Soft Science Fiction: Soft science fiction is the opposite classification to hard science fiction. In soft sci-fi the world is clearly a science fiction world, but the story either doesn't emphasize the science, choosing to focus on the characters, or it focuses on "soft science", like psychology and anthropology.
- Space Opera: In short, a space opera is the science fiction version of an actual opera storyline. There is high-strung emotion, intergalactic war, and almost always at least one love interest. the plots are very interwoven and tend to be complicated with many subplots.
Now, I won't touch on the romantic sub-genres, but they exist for all of the main genres. Paranormal romance is the largest speculative fiction roamnce sub-genre, but sci-fi romance and fantasy-romance exist as well. If I gather enough information on the romantic sub-genres I may explain those as well.
Horror is often considered a part of speculative fiction, but I don't necessarilty considr a part of this and may also cover that later.
Peace be with you,