Learning major chords is the first part of learning chord theory. To fully understand the formation of major chords, you need to be familiar with the notes on the fretboard, as well as major scales. If you are lacking in those areas, it’ll be best to review them first, otherwise you won’t understand the video.
Let’s define what a major triad is; a triad are 3 notes either played together. A major triad is played using the 1st (root) + 3rd + 5th notes of a major scale.
TIP: You can find the 3rd and 5th notes in the scale by count up FOUR semi-tones to arrive at the 3rd, and then count up THREE semi-tones to arrive at the final note in the major chord, the 5th degree of the major scale.
Here are a couple of examples on how you’ll use the above to form major chords: