Triad time hooray!
The basis of harmony comes from 3 note chords we call triads. There are Major, tiads, there are minor triads, there are diminished and augmented triads.
In this lesson we will look at the major triad only.
The construction of a Major triad is Root, Major 3rd, perfect 5th.
If you don't understand what that means you need to go learn about intervals and then come back to this.
There are only 3 notes in a triad.
Each string will have Root,3rd, 5th one time each within an octave.. Play just the notes of the chord up and down on one string then try the strings sets(3 strings at a time)
You will end up with 3 different shapes.. They are called Root, 1st inversion, 2nd inversion. That's it Easy right? Now move them accross to other string sets,
compensate for the B string! You are all set.
Finally, the I IV and V chords from the Harmonized major scale are all major triads.. Try playing the I, IV, and V chords from the C major scale. That would be Cmajor, Fmajor and Gmajor triads and notice that they contain the notes CEG FAC and GBD . together they include all 7 letters of the C major scale..
C major scale = CDEFGABC
Therefore the combination of these 3 major chords contain all the other chords in the major scale: the ii the iii the vi and the viidim. (3 minor triads and 1 diminshed triad.)
Also this would work from a minor perspective, the minor triads would contain within them all the material to generate the same scale therefore they contain within them all the Major triads.
Do your homework and practice a ton!