What is special about the day of `Ashura’? What is the significance of fasting the Day of `Ashura’?

About this day the Prophet (peace be upon him) said, “Fasting the day of `Ashura’ (is of great merits), I hope that Allah will accept it as an expiation for (the sins committed in) the previous year.” (Muslim)

In the video here Sheikh Waleed Basyouni provides answers to these questions, while reflecting on this hadith  …