ESRB

The Electronic Software Rating Board (ESRB) is the American organization which rates the games you play. In Europe it is the Pan European Game Information (PEGI) board. The ratings are as follows. Titles rated EC - (Early Childhood) have content that may be suitable for ages 3 and older. Contains no material that parents would find inappropriate. Titles rated E (Everyone) have content that may be suitable for ages 6 and older. Titles in this category may contain minimal cartoon, fantasy or mild violence and/or infrequent use of mild language. Titles rated E10+ (Everyone 10 and older) have content that may be suitable for ages 10 and older. Titles in this category may contain more cartoon, fantasy or mild violence, mild language, and/or minimal suggestive themes. Titles rated T (Teen) have content that may be suitable for ages 13 and older. Titles in this category may contain violence, suggestive themes, crude humor, minimal blood and/or infrequent use of strong language. Titles rated M (Mature) have content that may be suitable for persons ages 17 and older. Titles in this category may contain intense violence, blood and gore, sexual content, and/or strong language. Titles rated AO (Adults Only) have content that should only be played by persons 18 years and older. Titles in this category may include prolonged scenes of intense violence and/or graphic sexual content and nudity. Titles listed as RP (Rating Pending) - have been submitted to the ESRB and are awaiting final rating. (This symbol appears only in advertising prior to a game's release.)
 * EARLY CHILDHOOD
 * EVERYONE
 * EVERYONE 10+
 * TEEN
 * MATURE
 * ADULTS ONLY
 * RATING PENDING

Zelda Ratings
Although the Zelda games have been around longer than the ESRB, every main Zelda game has an ESRB rating due to rereleases. Every Zelda game has a rating of E (Everyone) except for Twilight Princess which is rated T (Teen).

ESRB.com