The major scale is the most basic scale in music. The notes from C to C, with no sharps or flats, make up a major scale. The whole/half step pattern is W-W-H-W-W-W-H. Other scales have sharps or flats added to maintain the same pattern of intervals. A major chord is made up of a major third and a minor third.
The minor scale is the second type of scale used in western music. It has three forms: natural, harmonic and melodic. The natural major scale has the interval pattern of W-H-W-W-H-W-W. The notes from A to A, which include no sharps or flats, make up a minor scale. The harmonic minor scale raises the seventh, while the melodic minor scale raises the sixth and seventh on the way up, and lowers them again on the way down. A minor chord consists of a minor third and a major third.
The main difference between the major and minor scale is the lowered third. For instance, an C major chord uses the notes C-E-G, while a C minor chord uses C-Eb-G. A major scale can be turned into a natural minor scale by lowering the third, the sixth and the seventh tones of the scale. For a harmonic minor, only lower the third and sixth. For a melodic minor, lower only the third on the way up and the third, sixth and seventh on the way down.