That is, for example the scale of A minor:
The interval is the 'gap' between two notes, so between A and B is a whole Tone, between B and C is only a Semitone, between C and D is a whole Tone, etc.
Each Minor scale is associated with a major scale by sharing the same notes. The key of A minor is the relative minor of C major - both can be played on the white notes of a piano starting with A or C respectively.
In folk music, the minor is often used as it has a sadness in its sound that is useful for ballads. The common minor keys are Am, Em, Bm (the relatives of C, G and D) and often a tune will modulate from major to minor and back again in a typical 2-part A-B tune.
The modern minor scale is based on the Aeolian Mode.