Fireborn: Dark Phoenix
Unlike standard Fireborn characters, characters in this game are one of the races of Taan, and deviate significantly from human norms.
Superhuman aspects (as written in the PHB) refer to an unusual level of power that this race has in the aspect denoted; each Superhuman aspect counts as an Automatic Success on any tests using that aspect. It does not count as part of the base aspect for any purpose, such as derived statistics (e.g. superhuman water does not grant extra wounds before dying). It does not necessarily represent literally unnatural ability; it may be a natural feature of a race.
Subhuman aspects refer to an usual level of weakness that this race has in the aspect denoted; for each subhuman aspect, the character takes a -1 penalty (and hence rolls one fewer die, or gains one fewer automatic success if they have any source of them) on all tests involving that aspect. It does not count as part of the base aspect for any purpose, such as derived statistics (e.g. subhuman water does not mean fewer wounds before dying).
If a character ever has a subhuman and a superhuman aspect in the same Aspect, they directly negate each other (i.e. they have no overall bonus or penalty).