Okay kiddo, sometimes there are things that are not necessarily bad, but they are only considered bad because people say they are. These things are called "malum prohibitum".
Imagine your teacher telling you that you can't bring your favorite toy to school, even though it's not hurting anyone. That toy becomes a "malum prohibitum" because it's not actually bad, but it's not allowed by the rules.
Sometimes, laws are made to say that certain things are not allowed, even if they are not inherently bad or harmful. These things can still get you into trouble if you do them, so it's important to know what they are and follow the rules.
Think of it like playing a game with your friends. Even if you don't think cheating is bad, it's still against the rules and can get you in trouble if you do it. Cheating is a "malum prohibitum" in the game, just like some things are "malum prohibitum" in the eyes of the law.