Today most non-Orthodox Jews celebrate a girl's Bat Mitzvah in the same way as a boy's Bar Mitzvah. Generally Bat mitzvah's are for 12 year old girls. All Reform and Reconstructionist, and most Conservative synagogues have egalitarian participation, in which women read from the Torah and lead services.

The majority of Orthodox Jews reject the idea that a woman can publicly read from the Torah or lead prayer services whenever there is a minyan (quorum of 10 males) available to do so. However, the public celebration of a girl becoming Bat Mitzvah in other ways has made strong inroads in Modern Orthodox Judaism and also in some elements of Haredi Judaism. In these congregations, women do not read from the Torah or lead prayer services, but occasionally they will lecture on a Jewish topic to mark their coming of age, learn a book of Tanakh, recite verses from the Book of Esther or the Book of Psalms, or say prayers from the siddur.

In some modern Orthodox circles, bat mitzvah girls will read from the Torah and lead prayer services in a women's tefillah. Rabbi Moshe Feinstein, a prominent Orthodox posek, has ruled that Bat Mitzvah celebrations are allowable and not be construed as imitating non-Jewish customs; however, they do not have the status of seudat mitzvah. Rabbi Avadia Yosef holds that it is a seudat mitzvah.

The brit milah (Hebrew: בְּרִית מִילָה‎ [bʁit miˈla], Ashkenazi pronunciation [bʁis ˈmilə], "covenant of circumcision"; Yiddish pronunciation, bris [bʀɪs]) is a Jewish religious male circumcision ceremony performed on the eighth day of a male infant's life by a mohel. The brit milah is followed by a celebratory meal (seudat mitzvah).

Yes, the boy is called 'a/the bar mitzvah' which translates as 'son of mitzvah'. For a girl, it would be 'a/the bat mitzvah' 'daughter of mitzvah'.

Grammatically, You say B'nai Mitzvah just as you would Bar Mitzvah or Bat Mitzvah.

The plural for a bat mitzvah is a b'nai mitzvah