With respect to games, in a nutshell, "high fantasy" means alien, bizarre, other worldly and "low fantasy" means slightly more realistic, less bizarre, less alien, possibly with more realistic characters or mature themes.
A world built on the bones of 8 dead gods who are trying to break free, where dancing on a tower can lead to a 1008 year period where time goes all fubar, where the sun is literally a hole in space, where we have hermaphrodic demi-gods that likes to pierce meteors and slay things with his "muatra", where we have walking, talking cat-people whose physical form is dependent on the phases of the moons whence they were born, where we have walking, talking lizard-people and sentient, psychic trees...
Oh yeah, and a dragon who's about to come
eat the world. Low fantasy much?