Harmonic Minor vs. Melodic Minor

Both of these start on C, and both keep the raised seventh that a plain natural minor doesn't have - the leading tone that pulls back to the tonic.

The wheel makes the difference positional rather than verbal: the sixth-degree wedge sits one wedge further clockwise in Melodic Minor, and the spoke drawn from the center recolors to the interval that degree now forms with the tonic. Everything else on the two wheels is identical.

That single degree is the whole reason Harmonic Minor has its stretched, almost Middle-Eastern gap between the sixth and seventh - a step and a half that no other common scale leaves open. Melodic Minor closes it by raising the sixth, trading that exotic leap for a scale that runs smoothly in both directions, which is the whole point of its name. Reading it is one thing; the difference is much more obvious held under a drone, which is what the links under each figure are for.