In simple terms, a criminal offence is an act that is against the law! All people have rights. The rights that a person has are all protected by the law. For example, one of these laws is that no person is allowed to injure another. If a person injures another, then that is against the law. This is then called the criminal offense [in German: Straftat].
There is a punishment for a crime. The punishments can vary. The extent of the punishment is also determined by the law. A judge decides on the punishment.