Okay kiddo, so imagine you are playing with your toys and your mom has to go to the store for a little while. She tells your older sister to watch over you and make sure you don't get into any trouble. That's kind of like what the regency acts were for the kings and queens of England a long time ago.
Sometimes, the king or queen would become too sick or too young to rule the kingdom on their own. So, just like your mom asked your sister to watch over you, the English Parliament (which is like a big group of important people who make decisions for the country) would assign someone to be in charge of the kingdom until the king or queen was able to take over again.
These people were called regents, and the laws that were created to give them power and make sure they did their job were called the regency acts. The regents had to make decisions that were in the best interest of the kingdom and follow the rules set out by the regency acts until the king or queen was back in charge.
So, just like you had your sister watching over you, the regency acts made sure that England had competent and responsible people in charge when the king or queen couldn't do their job.