andrew: I agree - VW's can be very cryptic and difficult to understand (unnecessarily so - ).
Perhaps a starting point for your education might be in in the document
VAG 873003 – How to Read Wiring Diagrams? This (hover your mouse over the acronym to see what it means) seems to be in the public domain, so you should be able to source it easily using Mr Google. I suspect that it's also available on
erwin.
Don