By Amy E. Feldman

PHILADELPHIA (CBS) - What do movie ratings really mean and who enforces them?

The movie Bully, successfully won its battle to have the rating lowered from R to PG-13. What are the definitions of those ratings? In a G-rated movie, there is no nudity, sex or drug use, and language might not be polite but consist of everyday expressions.

In PG movies, there is no drug use but may be some profanity and some depictions of violence or brief nudity. But nothing so intense as to require that parents be strongly cautioned.

PG-13 movies go beyond the PG rating in theme, violence, nudity, language, adult activities or other elements.

As for language, any more than one use of a particular sexually-oriented word, even if used as an expletive, will take a movie into the R-category although in cases like the movie Bully, a special vote of two-thirds of the rating board can decide to allow the PG-13 rating.

An R-rated movie can have adult themes or activity, hard language violence, sexually-oriented nudity, and drug use and children under 17 are to be accompanied by an adult. Interestingly, though the rating system suggests the appropriateness of a movie for a particular age group. The police don’t enforce who gets into a movie – it’s you, the parent, who decides.