There is the Nodes for Dummies discussion that isn't anywhere near as long. Decent intro to the mat room. BB has a word document on the essentials on VSS. But seriously, you can get a lot of your questions answered by first reading the bit of documentation that comes with VSS, and then, having a play. Don'tr try to understand the shader too much: just those things you can alter/modify.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks