Okay kiddo, so you know how when you get sick, your parents take care of you and make sure you are okay, right? Well, the government works kind of like that too. Each state has a leader (called a governor) who helps take care of the people who live there.
But, just like sometimes your parents might get sick or have to go away for a little bit and they can't take care of you, sometimes the governor might not be able to do their job anymore. It could be because they get really sick or have to go to a different job.
So, to make sure the state keeps running smoothly, there's a list of people who would take over if something happened to the governor. This list is called the gubernatorial line of succession.
Basically, if the governor can't do their job anymore, the person who is first on the list (usually the lieutenant governor) will become the new governor. Then, if that person can't do the job either, the next person on the list will take over, and so on until they get to the end of the list.
It's important to have this list so that the state doesn't get left without a leader and can keep taking care of the people who live there.