The Bar Mitzvah and Bat Mitzvah are a coming-of-age rite of passage in Jewish culture, when the boy turns 13 and the girl turns 12 or 13 (depending on the Jewish sect) and is then held fully accountable for all his/her actions instead of the parents.

It goes back thousands of years, but it is more of a social and cultural event than a religious one (it is never mentioned in the Torah).