Penal labour is when a person has to do a certain type of work as a punishment for breaking a law. For example, if you do something wrong like stealing or fighting and you get caught, the judge might make you do work instead of just sending you to jail. This could be something like picking up trash on the side of the road or working in a library. It's a way for people to pay back for the bad thing they did in a way that is not as hurtful as putting them in jail.