The presidential succession act is like a set of rules that tell us what to do if the president of the United States can't do their job anymore. If something bad happens to the president, like they get sick or hurt really badly or they pass away, then we need someone else to take their place and do the job of the president. The presidential succession act helps us decide who that someone else should be.
The first person in line to be the new president would be the Vice President. If the Vice President can't do it for some reason, then the next person in line would be the Speaker of the House. And if the Speaker of the House can't do it, then we go down a list of other people in important positions in the government until we find someone who can do the job.
This is all very important because we need someone who can lead our country and make important decisions if something happens to the president. We want to be prepared and have a plan in case something bad happens, so that we can keep our country safe and strong.