Aliyah To The Torah
The widespread practice is that on the first Sabbath of his thirteenth year, a boy is called up to read from the weekly portion of the Law (five books of Moses), either as one of the first seven men or as the last, in which case he will read the closing verses and the Haftarah (selections from the books of the Prophets); and if he is unable to read, to recite at least the benediction before and after the reading. (Calling someone up to say the Torah blessings during a service is called an Aliyah, from the Hebrew: עֲלִיָּה, from the verb la'alot, לעלות, meaning, "to rise, to ascend; to go up"). He may also give a d'var Torah (a discussion of some Torah issue, such as a discussion of that week's Torah portion) and/or lead part or all of the prayer services.
In non-orthodox circles, the above applies to a girl at the time of her Bat Mitzvah as well. In Orthodox congregations, a Bat Mitzvah ceremony will not include the Bat Mitzvah girl leading religious services, as women are ineligible to lead communal religious services in the Orthodox tradition. Some progressive Orthodox congregations do allow women, including Bat Mitzvah girls, to read Torah or lead prayers at women-only prayer groups. Precisely what the Bar/Bat Mitzvah should lead during the service varies in Judaism's different denominations and from one congregation to another and is not fixed by Jewish law.
In Orthodox circles, the occasion is sometimes celebrated during a weekday service that includes reading from the Torah, such as a Monday or Thursday morning service, in which case the Bar Mitzvah will also lay tefillin for the first time publicly.
Some communities or families may delay the celebration for reasons such as availability of a Shabbat during which no other celebration has been scheduled, or due to the desire to permit family to travel to the event. However, this does not delay the onset of rights and responsibilities of being a Jewish adult which comes about strictly by virtue of age.
Read more about this topic: Bar And Bat Mitzvah