In Jewish tradition, a boy becomes obligated in the commandments at age 13 as a bar mitzvah.
The age refers to Jewish legal adulthood rather than the party or synagogue service itself. A boy reaches this status when he completes his thirteenth year according to the relevant Jewish calendar calculation. From that point, he is considered responsible for his own religious obligations.
The public ceremony developed later than the underlying age rule. Communities commonly mark the transition with a Torah honor, a speech, communal prayer, and a celebratory meal. Customs vary among Orthodox, Conservative, Reform, and other Jewish communities.
A common mistake is to treat “bar mitzvah” only as the event. Strictly, it also describes the person who has reached this stage; “bar” is Aramaic for “son,” and “mitzvah” means commandment.