The Natural or Pure Minor scale (aeolian mode) is the sixth degree of the Major scale.
The Natural Minor scale contains besides the minor third (Eb) a minor sixth (Ab) and minor seventh (Bb). The minor sixth gives the scale a very velvety dark sound.
The Natural Minor scale and the Major scale are parallel scales and contain in each case the same notes and key signatures. The Natural Minor scale is always a minor third lower than the Parallel Major scale. With the circle of fifths on the utilities color circle you can easily read off the Parallel Major and Minor scales with their key signatures.
A-Natural minor (Root note of the chord less minor third)