Let's start with this:
I know the top image is of a flyback diode. I also get that its purpose is to protect the power supply from a voltage spike when the electromagnet releases. So I've gotten that far.
The second diagram is what gets me, I guess. In this diagram, I am assuming the diode is being used in a more conventional setting and it is wired inline (in series?)" The cathode stripe in this picture, though, is toward the negative end of the circuit, which is exactly the opposite of the way it is being used in the former picture. So, that's confusing to me. Why is the polarity different between the two? Also, why do I need to wire a flyback diode in parallel? Shouldn't I just be able to put it inline in the positive wire to protect the voltage source? (And at that point, would I put the cathode end toward the solenoid?
I'm just trying to wrap my head around orientation and application here. I see lots of videos explaining how they act as "valves" and can rectify AC current, but very little about how flyback diodes work (and why they are wired in parallel).
Still getting my sea legs, here. Thanks for any helpful input.