Some definitions in the genre
Fantasy — largely mythic and Celtic in inspiration, deals with dragons, magic swords, and chalices that glow in the sky. Examples include "The Lord of the Rings" and the Harry Potter series.
Science Fiction — deals with technologies we don't yet have, other universes. Examples include "Star Trek" and "Star Wars."
Speculative Fiction — deals with this planet, doesn't use things we don't already have or are not already developing. 'Beam me up Scotty' is not speculative fiction. We don't yet have the ability to disintegrate people and have then reassembled in some other place.
— Margaret Atwood, quoted in the NY Times, 24 June 2003 (my paraphrase)