Two fish.
Significance of the Month
Adar is the 12th and final month of the Jewish calendar. The Talmud teaches, "When the month of Adar comes we increase our happiness." Adar is known for its frivolity and joy, because in it we celebrate the holiday of Purim and we begin preparations for Passover. Adar is so fun that during a leap year we get to do it twice.
To compensate for the fact that the lunar year is eleven days shorter than the solar calendar, the rabbis developed a way to include an extra month in the year to ensure that the months fell in their proper season. During a leap year, the month of Adar is repeated and we observe Adar I and Adar II. In this situation, Purim falls during Adar II.
Holidays
Adar contains a number of special Shabbatot on which special Torah portions and haftarot are read. The Shabbat immediately before Rosh Chodesh Adar is known as Shabbat Shekalim, on which we learn about the Half-Shekel that every Jew had to donate to the Temple. The Shabbat before Purim is called Shabbat Zachor (Remember) on which we read of the atrocities done to the Israelites by the nation Amalek, and the commandment to erase all memory of Amalek. Haman, the villain of the Purim story, is descended from Amalek. The Shabbat after Purim is known as Shabbat Parah, and we read about the ritual of the Red Heifer which purified people who had become ritually impure through contact with the dead.
The Fast of Esther is on the 13th of Adar. This day commemorates the fast that Esther imposed on the Jews of Shushan before she beseeched King Achashverosh to save the Jews from Haman.
Purim falls on the 14th of Adar and celebrates the heroine Queen Esther, who saved the Jews of Persia from the evil Haman. Purim is the holiday of hidden miracles, on which we read the book of Esther. Jews wear costumes on Purim to show that like the Book of Esther, one must go beyond the surface appearance to gain a true understanding. We are commanded to give charity to the poor, send packages of food to friends and family and to have a festive meal.