If someone is found guilty of a crime, their punishment may be to pay a fine, a certain amount of money. In many countries, fines can be ordered by police, court judges and some government officers.
When agreeing to a contract with a business, a customer may agree to certain rules. If the customer breaks the rules, then they agree to pay a fine for doing so. For example, when somebody hires a car and agrees to return it by Friday, they agree that if they do not return the car by Friday, they must pay a $50 fine to the business.