Short for Entertainment Software Rating Board, ESRB is a rating system that helps enable parents and others choose games that are most appropriate for their children. The picture is an example of the Sims 3 expansion pack "Ambitions" and an example of the ESRB TEEN rating on the box.
Listing of ESRB ratings
Below is a list of the ESRB rating symbols, and a description for each.
Short for "early childhood," EC games are best fit for children under the age of 3.
Short for "everyone," E games are games that are good for people of all ages.
Short for "Ages 10 and up," E10+ are games that may contain mild violence, mild language, and suggestive themes.
Short for "teen," T games are games that are best for anyone over the age of 13.
Short for "mature," M games are best for anyone over the age of 17.
Short for "adults only," AO games are games that are best for anyone over the age of 18.
Short for "rating pending," RP is games with a rating that is still under investigation. If the game is likely to be mature, the ESRB RP rating may also include "Likely mature 17+."