MPAA Film Rating System
MPAA - stands for Motion Picture Association of America
"The Motion Picture Association of America's film-rating system is used in the U.S. and its territories to rate a film's thematic and content suitability for certain audiences. The MPAA system applies only to motion pictures that are submitted for rating. Other media (such as television programs and video games) may be rated by other entities. A voluntary system not enforced by law, it is one of various motion picture rating systems used to help parents decide what movies are appropriate for their children."
Wikipedia: MPAA Rating System
There are 5 different MPAA Ratings which I have listed below:
G — General Audience: - All ages admitted.
PG — Parental Guidance Suggested: - Some material may not be suitable for children.
PG-13 — Parents Strongly Cautioned: - Some Material may be inappropriate for children under 13.
R — Restricted: - Children Under 17 Require Accompanying Parent or Adult Guardian.
NC-17 — No One 17 and Under Admitted.
Wikipedia states that: If a film is not submitted for rating, the label NR (Not Rated) or Unrated is used. However, this is not an official MPAA classification. Films not yet rated by the MPAA, but that are expected to be submitted for rating, are often advertised with the notice "This Film is Not Yet Rated".
What Each Rating Means
MPAA - More Information