The harm principle says that people should be free to do whatever they want as long as it doesn't hurt anyone else. This means that if someone wants to do something in their own home, away from other people, they should be able to do it as long as it doesn't hurt anyone else. For example, if a person wants to play loud music in their house away from other people, they should be able to do that without the government punishing them for it. However, if that person's loud music is bothering their neighbors, then the government might step in and tell them to be quieter. This is because the loud music is hurting someone else, so the government will try to protect the people who are being harmed.