Watch the SECTION 1: Essential Concepts online guitar lesson by Angus Clark from Hard Rock Survival Guide: Rhythm
The Essential Concepts section of this course is very diverse. Some of the segments are very basic, some are more nuanced or advanced. When a player works, you refine elements of your technique in order to meet the needs of the various gigs you get hired for. At the same time, it's mastery of the fundamentals that gives you the flexibility to get the gig in the first place. Refining an element of your technique is easy when you control the fundamentals. Without the fundamentals you are sunk. So don't skip around - take some time with this. You can always jump to the performance section and then jump back to these concepts for the explanation of the fundamentals at play in the various performances. That's ok. But at some point you'll have to visit all the concepts and just let it all sink in, even the triads.