Hello, I'd like to ask you about the mission planner log

Thanks to the masters, I’m learning one by one.
Thank you so much.
When we fly quadcopters, we sometimes fall down due to unexpected events, and if we fall, we’ll see logs on the mission planner, but I’m not sure what to see because there are so many items. I’d really appreciate it if you could pick the most important points and let me know one by one by one.

You may start from the ardupilot wiki page

Or have a look at the seminar by devs