Established in 1994, the Entertainment Software Rating Board (ESRB) has become the de facto standard for rating video games. While the ratings differ from those used for movies, they both follow a similar formula of relating the ratings to age.
Along with the rating, the ESRB assigns content descriptors to each game. This allows parents to better judge why a video game got a rating and whether or not it might be appropriate for their child. Content descriptors range from the relatively benign like "cartoon violence" to mature descriptors like "blood and gore" and "partial nudity".

ESRB Ratings: EC - Early Childhood
Games marked with the "Early Childhood" rating from the ESRB contain content that is entirely appropriate for children ages 3 and older. This rating is similar to a "G" rating for a movie. "Early Childhood" games have no content that would be considered unsuitable for a child including no mild themes such as crude humor or cartoon violence.

ESRB Ratings: E - Everyone
Games marked with the "Everyone" rating from the ESRB contain content appropriate for children ages 6 and up. This rating is similar to a "G" rating for a movie, but may contain some slight material that could be inappropriate for a toddler aged 3 to 5. Common reasons for a game to have the "Everyone" rating include mild cartoon violence, mild fantasy violence and mild crude humor.

ESRB Ratings: E10 - Everyone 10
Games marked with the "Everyone 10 " rating from the ESRB contain content appropriate for children and teenagers ages 10 and up. This rating is similar to a "PG" rating for a movie. Some parental guidance on mildly suggestive themes could be necessary. Common reasons for a game to have the "Everyone 10 " rating include mild violence, mild suggestive themes, mild language, cartoon violence or crude humor.

ESRB Ratings: T - Teen
Games marked with the "Teen" rating from the ESRB contain content appropriate for teenagers ages 13 and up. This rating is similar to the "PG13" rating for a movie. Common reasons for a game to have the "Teen" rating include violence, suggestive themes, crude humor, minimal blood and mild use of strong language.

ESRB Ratings: M - Mature
Games marked with the "Mature" rating from the ESRB contain content appropriate for people ages 17 and up. This rating is similar to the "R" rating for a movie. Common reasons for a game to have the "Mature" rating include intense violence, blood and gore and sexual content.

ESRB Ratings: AO - Adults Only
Games marked with the "Adults Only" rating from the ESRB should only be played by people aged 18 and up. This rating is similar to the "NC-17" and "X" ratings for a movie. These games have been deemed inappropriate for children and teenagers. Common reasons for a game to have the "Adults Only" rating include extremely graphic and prolonged violence, graphical sexual content and nudity.

ESRB Ratings: RP - Rating Pending
Games marked with the "Rating Pending" rating from the ESRB have been submitted to the ESRB but have not yet been rated. These are generally games that are not yet released to the public or available for purchase.