I know the relationship between Major Scales and Minor Scales(Natural Minor Scales), A Minor Scale is built starting from the sixth note of the relative Major Scale .i.e.

A minor Scale is relative to C Major Scale
B minor Scale is relative to D Major Scale

(W-H-W-W-H-W-W - > W-W-H-W-W-W-H)

But what are these Harmonic Minor Scale, Melodic Minor Scale. How they are different from Natural Minor Scale and why they are important. Apart from these is there anyother type of Minor Scale.