This is a pretty good site for scales and modes,
http://docs.solfege.org:81/3.14/C/scales/modes.html (Double Harmonic minor is the 4th degree of Double Harmonic Major) Obviously there are other names used for scales and modes etc.. Each scale has its own page with more info.... but good starting place.
Does not talk about function of chords derived from scales, I'll try and find more information on that subject. Reg