Dude you picked up a later chapter in an advanced Calculus book without taking Arithmetic, Geometry and Algebra first. All of your inquiries have many months of prerequisite knowledge!
Chord scales are the basis of ALL MODERN HARMONY - Major, Minor and Modal. Do you know all your major scales in all 15 keys, all the intervals in all 15 keys, all the triads in all 15 keys and their function? What is a vi ii V i progression in Ab major? What is an inversion? A chord scale is a scale made out of chords - but what chords and how do you derive which ones to use?
You cant just pickup MODULE 4 with no background whatsoever - that is why there is MODE ONE TWO AND THREE - way before anyone gets to module 4. Did you complete MODULE ONE first? Yeah? Show us THAT. Make a video of you playing all the exercises in MODULE 1. Lets see that first!