Every automation, no matter how fancy, breaks down into the same skeleton: a trigger (something that starts the flow — a new email, a form submission, a schedule), a series of steps (actions, filters, AI calls) that each take input and produce output, and data mapping between those steps that says "this field from step 2 becomes this field in step 3." Run history is the log of every time the automation fired, showing exactly what data flowed through each step.
Most people think about automations in terms of what they do ("it processes my emails"), but the moment something breaks, you need to think about them in terms of their skeleton: which step failed, what data did it receive, and what did it try to pass on. Learning to see the skeleton instead of the magic is what separates people who can only build automations from people who can also fix them.