Any two or more notes sounded simultaneous are known as a chord. The most frequently used chords are triads, so-called because they consist of three distinct notes stacked vertically in thirds. The lowest-pitched tone being the root, then comes the third, and the fifth, which is the highest.
You can find bellow the illustrations of all Major Triads and also information about triads types and triads inversions.
The melodic minor scale has a particularity. It has two forms: ascending and descending. Ascending one has the same notes as the natural minor scale, except that the 6th and 7th degrees are raised by one Semitone (1/2 step). This changes creates a Major 6th between 1st degree and the 6th degree and also a Major 7th between 1st degree and the 7th degree.The 7th degree becomes Leading Tone in both, Harmonic and Melodic version. The descending melodic minor is just another name for the natural minor scale.