Shushan Purim

Purim is observed in some places exclusively on the 14th of Adar (Purim) and in others, exclusively on the 15th (Shushan Purim).

Why do we celebrate Shushan Purim?
The reason for the different dates is that whereas Jews in Shushan waged war on both the 13th and the 14th of the month, and observed the 15th as a day of festivity, in all other provinces the Jews waged war on the 13th and observed only the 14th as a day of festivity.

What are the customs of Shushan Purim?
It is observed in the same way as Purim and the Megillah (scroll) of Esther is also read on this day.