Back in the day before trade institutes existed you needed to have a mentor to learn a skill.
At the time, everything came through experience and first hand expertise, there weren’t Youtube videos, or even numerous books, on how to learn skills like smithing or carpentry.
But, since the advent of trade institutes, the mentor method of studying a trade has gone by the wayside, regulated out of existence or almost. The government states you need standardized tests to prove your level of skill, which seems too much. I was lucky enough to have a mentor who educated me on the basics of Heating, Ventilation & A/C jobs when I was still a teen. My next door neighbor was a guy named Big Ed, and he did mobile heating repairs out of his truck. Big Ed was self taught, and knew everything there was to do with ductwork and furnaces. He entirely made his own sheet metal in his workshed, so that he could craft his own custom air ducts. Big Ed did not understand anything about air conditioning, that was “after his time” he always said. But, he taught me the basics of heating repair, and the skills I needed to make my own ductwork. After graduating high school, I’d go to the HVAC institute to become certified respectfully, and that is where I started studying about air conditioners. I was already well skilled in heating systems and ventilation systems, however I had a lot to learn about AC. My mentor educated me a lot, however I got the rest of the way through my experience.