The musical scale that differs from the major scale in that three of the tones are flatted a half-step. It is identical to the Aeolian mode of the major scale.
For example:
  • A Natural Minor contains the notes: A B C D E F G
  • F# Natural Minor contains the notes: F# G# A B C# D E
  • D Natural Minor contains the notes: D E F G A Bb C
Based on the intervals between the notes, the standard triads used when playing a piece in a minor scale follow the pattern:
minor, diminished, major, minor, minor, major, major.

Specifically, if you were to looking at a classical piece in A minor, the chords would (probably) be as follows:

 i   ii0   III  iv  v    VI    VII
Am  Bdim    C   Dm  Em    F     G
Am7 Bm7b5 Cmaj7 Dm7 Em7 Fmaj7 Gmaj7
Not a very exciting scale. I know a guy who's vehemently opposed to using the sixth tone of the scale when playing it, because it makes it sound very slightly like you're playing the relative major scale. I find it most interesting to throw in extra notes, in order to jump back an forth between natural minor and the harmonic minor scale, and/or the minor blues scale.