A major triad has a major third followed by a minor third. A minor triad has the minor third first and then the major third. Watch the lesson to hear the triads for a C major scale and its relative minor A. The chords (triads) are mostly the same. In C major you'll use a lot of C, F and G chords. In A minor you'll use lots of Am and Dm chords.
Here are some of the previous lessons if you need some background information or a refresher:
I, IV and V chords
major and minor thirds
