What do they do in a bar mitzvah?

A bar mitzvah is wherever the boy in question is when he turns 13. If you're referring to the ceremony held to celebrate a boy becoming a bar mitzvah, that is normally held in a synagogue.

A Bar mitzvah is when a Jewish boy turns 13 and becomes an adult. As part of the customary rite of passage he will read from the Torah in the synagogue.A Bat mitzvah when a Jewish girl turns 12 and...

Yes! There are a number of reasons for having an adult Bar Mitzvah - you may not have celebrated it when you were a child, you may have converted in later years, or you may have experienced a...

After the bar mitzvah there is sometimes a food reception in the synagogue, especially if the bar mitzvah takes place on Shabbat (which is most common).

There is no specific symbol for a bar mitzvah.