Let's look at how chords are formed. Chords can be directly related to scales. Major chord are formed of notes inside the major scale. More precisely, the root, third and fifth. Let's take C as an example, the notes of the C major scale are C D E F G A B C. The root would be C, the third E, and the fifth G (that's a triad). Now, I told you you'd understand why there are minor and major scale when they can be equivalent. Altough the A minor scale has the same notes as the C major, the root third and fifth is different. The root is A, the third C and the fifth E. Ok, turn to the next page, we'll go see key signatures.