Q:
A: I did, but I'm assuming that's not the question. As others have pointed out, you don't "have" a Bar/Bat(Bas) Mitzvah, you become one. What this means (besides for the literal translation of "Son/Daughter of the commandments") is that (s)he now has the privileges and responsibilities of an adult according to Jewish law now that they've come of age (12 for a girl, 13 for a boy). I noticed that some people mentioned the privileges, i.e. for men- being counted towards a forum and being able to lead the services, but no one mentioned the responsibilities. One goes with the other, it's a two-way street. An adult Jew has many responsibilities, starting with him/herself. A male has to start praying daily and keep his commandments, and a female has to keep her commandments and learn the things which will apply to her (those that know, know). Because of the tremendous responsibility being put on people at this age, and to celebrate what they've become, i.e. a full-fledged member of the Jewish people, most people celebrate in some way, some more than others. In keeping with Jewish tradition, men, who are more external by nature will have a large party and read the Torah while women, who are more internal by nature, will have a more private celebration with friends and family. Oh, and just a little FYI, the reason why the girl comes of age younger is because Judaism recognizes that women mature faster.