Laylat al-Qadr, known in English as the Night of Power or Night of Destiny, commemorates the night in 610 CE when the first verses of the Qur'an were revealed to the Prophet Muhammad. Many Muslims celebrate the night on this, the 27th day of Ramadan, though others observe the 19th or 23rd day of Ramadan. The angel Gabriel spoke to Muhammad, commanding him to recite those first verses, and this became the beginning of the prophet's mission. Muslims believe that God's mercy and blessings are abundant on this night, and that one's fat for the upcoming year is decided, and so many Muslims read the Qur'an and practice Ehyaa, or night prayers to God for forgiveness and mercy. See also this site, this site, and this site.