Here is a chart of 7 and 8 note scales in relation to the Major Scale. As example, you flat the 3rd note of the Major, you get the Melodic Minor. If you flat the 3rd while retaining the original 3rd note, you get the 8-note Katagyllic.

To form the Harmonic Minor, you flat both the 3rd and 6th notes. and the difference between the 8-noted Manyllic or Bebop Minor is whether the original 3 or 6 is retained.