The word "Purim" means "lots" and thus refers to the lottery that Haman chose for the date of massacre. Thus Purim is celebrated on the 14th day of Adar, which is usually observed in the month of March. The 13th of Adar is the day which Haman chose for the extermination of the Jews, and it is on that day only when that the Jews battled their enemies for their lives. Thus on the 14th, they celebrated joyously for their survival. Thus the cities that were walled at the time of Joshua, Purim is observed on the 15th of the month, because the book of Esther says that in Shushan (a walled city), deliverance from the massacre would not be completed until the next day. Thus the 15th day is referred to as Shushan Purim.
However a leap year can witness two months of Adar, thus Purim is observed in the second month of Adar, so it is always one month before Passover. The 14th day of the first Adar in a leap year is thus celebrated as a minor holiday called Purim Katan, which means "little Purim". Though there are no specific observances for Purim Katan; however, a person should celebrate the holiday without mourning or fasting.In fact some other communities also observe the "Purim Katan" on the anniversary when their community was saved from a catastrophe, evil, destructionor oppression.
The Purim holiday is generally preceded by a minor fast, the Fast of Esther, which honours the Esther's three days of fasting which was observedas a preparation for her meeting with the king. Further, custom and tradition that are observed related to Purim is to hear the reading of the book of Esther. The book of Esther is commonly known as the Megillah, which means scroll. Although there are five books of Jewish scripture that are collectively referred to as Megillahs (Esther, Ruth, Ecclesiastes, Song of Songs, and Lamentations), this is the one which people usually refer to when they speak of the Megillah. Moreover it further customary to boo, hiss, stamp feet and rattle the gragers (noisemakers) whenever the name of Haman is mentioned for the whole purpose of this custom is to "blot out the name of Haman".
Other customs which are well associated with the observance of Purim is that of feasting, drinking and that of merry-making. For according to the Talmud, a person should drink until he cannot point out the difference between a "cursed be Haman" and a "blessed be Mordecai", though opinions may vary from person to person. Again a person certainly should not become so drunk that he may violate other commandments or can get seriously ill. However there is an exemption for those recovering alcoholics or others who may suffer serious harm from alcohol.
In addition to the feasting and merry-making customs, sending out gifts of food or drink have also become a customary affair.Thus the sending of gifts of food and drink is referred to as shalach manos (sending out portions). Moreover amongst the Ashkenazic Jews, a common treat at this time of year is that of the hamantaschen (Haman's pockets). These triangular fruit-filled cookies are the replica of Haman's three-cornered hat. Making charitycan also be referred as a common custom observed during Purim.
Other customary affair observed in order to celebratePurim is to hold carnival-like celebrations.Various plays and parodies are also performed in order to entertain the present audience and many beauty contests are also held. Thus it can be said that sometimesAmericans refer to Purim as the Jewish Mardi Gras.