A sub division of time in music. It is easier to keep up with a piece of music by counting measures as opposed to individual beats. Jazzers utilize the ascending mode most often and usually refer to the Melodic Minor in it's ascending mode. A succession of single notes played one after another. Less than major.
Minor scales are also popular and essential in Jazz.
The minor sound, for most listeners, is darker and has more tension than major sounds. For the beginner the use of the term minor can be confusing. This stems from the fact that most beginners think of minor as it applies to the minor chord only, i.e. Em, Gm, etc. Pat Martino uses this approach with much success. Different octave segments of the same diatonic scale.