Laylat al Qadr is a special night that falls within the last 10 days of Ramadan.
It's variously translated as Night of Power, Night of Destiny, Night of Decree and other names, and commemorates the night when the Qur'an was first revealed to Muhammad.

it is recommended to make extensive supplications (dua) on this night. One of the best dua that may be recited on Laylat al Qadr is that which the Prophet taught to his wife Aa'ishah.
He told her: "Say 'Oh Allaah, You are forgiving and You love to forgive, so forgive me.'"