The first thing I thought when I saw the chart (diagram 1) was, “Wow, that’s not ‘three chords and the truth!’ Maybe 20 chords and the truth.” ...

This is a root-fifth diad, but everyone calls them 'power chords'. In a chord chart, it would be notated as G5. The last step is to make it sound cool. It's a moveable shape common in rock and metal - ...