Ashura

The Day of Ashura of Ashura is the same thing and this day is followed the Islamic calendar. This day is very important for Muslim but it very important for Shia Muslim. The Muslims are divided into two parts and one is Sunni and another Shia. Ashura is celebrated by Shia Muslims on the 10th day of the Mahram of the Islamic Calendar. According to Quran or Hadith, this day does not get a specialty. Shia community does some work in the Ashura which is fully un-Islamic and unlawful by Islam. That is why, Sunni Muslims do not congregate at the festival of Ashura.
But Shia Muslim deny accepting this statement and they feel the sorrow for the tragic events of the Karbala where Husain was killed by a group of people. Sunni Muslims feels sorrow for the event but they do not do anything unlawful work. Shia Muslims cut their own body by sharpen knife and it is not permitted by Islam to harm anyone or own. India and Bangladeshi Shia Muslims do this by emotionally. Many Sunni Muslims pray of Hussain and they ask forgiveness in this day. It is celebrated in Iraq, Iran, Bahrain etc. You can learn many things from https://en.wikipedia.org/wiki/Day_of_Ashura link.