I grew up sniffing exhaust and listening to a motor telling you things also!
When it comes to the New Computer cars, I was lucky to have a Nephew who trained as a tuner...I understand the basics, that's it...I can use and understand a basic programmer, or know what KNOWLEDGEABLE people are doing....that's it!
GM sets up a car to meet noise requirements, warranty lengths, and reliability standards.
This means, that there is more Meat on the Bone!
Timing can be advanced or retarded, shift points, harder/firmer shifts, you can add more gas or lean the car out, etc., etc., all across the RPM range....and for different setups, weather, etc.
Then if you start adding performance parts, you need to tune to take full advantage of them...same with Blowers, Nitrous, Turbos, etc.
You can also check codes, run diagnostic, change tire sizes, and more.
I had Ted J do my last tune on my 2012...he sent me a "canned" tune in a SCT handheld...to me that tune woke my car up...but then, I hooked the handheld back up and data logged for him and sent him the info over my home Computer...and then, he used that info and sent me another tune back to my home computer...and I downloaded it into the Handheld....when I put that tune into my car, THE THING BECAME A BEAST!
So I came from sniffing exhaust, and adjusting carbs to understanding the basics of computers and actually datalogging!
lol Miracles do happen!!!