The clearest explanation of the differences between fantasy and surrealism I've yet to see comes from Ursula K. Le Guin's essay "The Critics, the Monsters, and the Fantasists."
3 Steps to Tell Surrealism from Fantasy Fiction

The clearest explanation of the differences between fantasy and surrealism I've yet to see comes from Ursula K. Le Guin's essay "The Critics, the Monsters, and the Fantasists."
Thankfully, the definition of speculative fiction simple: Speculative fiction is any storytelling possessing elements that aren’t feasible based on modern technology or elements that cannot be explained by modern science.