In Crowd # 4 (Big Dog Comics 2013)

E or A - Everyone or All Ages: Just like it sounds, these comic books are appropriate for children of any age. They are often aimed at the youngest readers

T - Tween: Generally suited for anyone over the age of 9

T+ - Older Teens: Best for ages 13 and up

M or PA - Mature or Parental Advisory: Comic books with this rating should not be sold to anyone under 18 without parental consent