system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the difference between fantasy and science-fiction?
gpt
It can be something of a spectrum with significant overlap, but principally, Science Fiction takes an existing scientific principal and expands on it in to explore the consequences, possibly hand-waving the specifics of the egineering, but generally holding to the accepted laws of the universe with specific scientifically justified exceptions.

Fantasy includes clear impossibilties that are not even attempted to be justified by modern, real science, but instead are justified internally by "Magic", where "Magic" is an aspect of the in-story universal laws are fundamentally different than our scientific understanding of the real world.