The Festival of Purim recalls the saving of the Jews that lived in Mesopotamia (Babylonia) under the Persian Empire, around the 5th century before the Common Era. The story goes that an influential Jew-hater by the name of Haman had carefully planned a nationwide massacre of the Jews, but due to clever intervention or Queen Esther and her uncle Mordechai, the Jews escaped this gruesome fate.
At the very beginning of the Purim evening service, the following psalm (Psalm 22) is read:
The story of Esther is full of exciting intrigues and unexpected turns and, without a doubt, belongs to the greatest treasures of world literature.
On the Festival of Purim, the following traditions are observed: 1) A public reading of the story of Esther (the "Meghilla") from a scroll, 2) Sending minimally two prepared items of food to at least one friend, 3) Giving charity to two or more poor persons, 4) Having a festive meal, 5) Finally, there are additions to the daily prayers.
Here is a recording (with translation and illustrations) of the book of Esther, with the accompanying berakhot (blessings) that are said before and after the reading: