I am going over the basics of Music Theory, and for some reason I am racking my brain between the actual differences between these two. Based on what my Music teacher was telling me is that one is based on Modal music (hence dorian mode), and the other one is different. The only thing I get at is that with Modal music the basic structure of wwhwwwh is just shifted so whwwhw (if I did that correctly, but just using it as an example), where as with the Harmonic minor that structure is actually different. I am trying to get the basics of harmonies and knowing what chords can be substituted for one another. I am trying to get to the point where I can build my jazz vocabulary and be able to improv over anything. Maybe someone can help me, I just feel like I am moving slow on learning this stuff.