Every major key has a relative minor key which is related to it — kind of a “kissing cousin” — by the same key signature. For example, the key of C major and A minor both share the same key signature — no sharps and no flats. Playing the A natural minor scale is like playing the C major scale, but playing it from A to A instead of from C to C. Parallel minor scales are those which begin on the same root — such as C major scale and C minor scale. Major and minor key signatures are the same, naturally — Eb major scale has 3 flats while C minor scale (it’s relative minor scale) also has 3 flats. Major & minor pentatonic scales work a little differently, and will be taken up separately at another time.