The reading of the Megillah on Purim is an obligation for each and every man and woman over the age of Bar or Bas Mitzva, both on the evening of Purim and again in the morning. Even children, as soon as they as they can appreciate the miracle of Purim should preferably hear Kerias Hamegillah.
Chazal are very stringent about this Mitzvah. If someone fails to hear even one word of the Megillah, They have not fulfilled their obligation.
Since everyone must make sure to hear each and every word from the Megillah, it is recommended that a person acquire his own kosher Megillah. In this case, if he should fail to hear a word being read by the Bal Koreh, he can read those words of the Megillah to himself, thereby fulfilling this important Mitzva properly.
Just as with Tefillin & Mezuzahs, various Kesavim (customs of writing) exist, so too with Megillos, There are Bais Yosef, Arizal, Sefardi, and Chabad.
Megillos come in various sizes. On average, the height of a Megillah is approximately 15 inches. The number of lines on each Amud (page) vary too. On average, they have 28 lines each.
However, some insist on acquiring a Megillah which consists of 11 lines on each Amud. The reasoning behind this is that the Gra writes that the letters of the names of Aseres Bnei Haman (the names of the ten children of Haman) should not be written in a larger size font than the rest of the Megillah. The only way to fulfill the custom of writing the Aseres Bnei Haman on a separate Amud, and not writing any of the letters any bigger, would be to write the entire Megillah on 11 lines perAmud, thus having the Aseres Bnei Haman uniform in size like the rest of the Megillah.
Some are of the opinion that it’s not necessary to write the Aseres Bnei Haman on a separate column . The Minhag of Chabad is to write the Megillah on 42lines,and the Aseres Bnei Haman are not written on a separate Amud. This Minhag stems from the layout of the Megillos written by the Rebbe Maharash, it is known that the Rebbe Maharash wrote a Megillah for each of his children.
Sefardim have the custom of adding on a wooden handle to their Megillos.