The BBFC classifies films into age categories to determine who can view movies. They use ratings like U, 12A, 15, and 18. A U film is suitable for ages 4 and over and contains no sexual references or strong violence. 12A films are not suitable for those under 12 without an adult, and can contain discreet nudity and sex. 15 rated films prohibit those under 15 and contain strong language and violence but minimal discrimination. 18 rated films are only for ages 18 and up and can contain any content.