Okay kiddo, have you ever heard of lying? It's when someone tells you something that isn't true. Well, pious forgery is kind of like lying, but it's when someone makes a fake document or object to make people believe in something religious.
For example, let's say there was a person a long time ago who wanted people to believe that a certain holy person did something really cool. Maybe they'll make a special book that looks really old with stories about that holy person doing heroic things that never really happened.
This might not seem like such a big deal, but it actually is! Pious forgery tricks people into believing things that aren't true, and that can have a big impact on people's lives and beliefs. It's important to always be truthful so we can trust what we believe is real.