In many cases, you can replace a minor chord (1-3-5) with a minor 7, minor 9, minor 11 or minor 13 chord. These extended minor chords simply give you "more" or "different" colour into to your music. I look at these as colours - sometimes I go for a minor 7 chord and another time, a minor 9 chord might sound nicer. This is completely subjective, of course. As a musician, you decide what you think fits the situation best, based on your personal experience and personal taste. These are chord voicings with the natural 9th on top. The theory behind a minor 9 chord is that you play the root, minor 3rd, 5th, minor 7th and 9th intervals together. However, as guitarists, we often ignore some of that theory, because 5 note (or more) chords don't work so well on guitar. So, you can view these voicings as minor 9th chords, even though some don't have the minor 7th and some don't have the 5th, etc. However, they will still FUNCTION as a minor 9th chord.