It is the Night when the first verses of the Quran were revealed to the Prophet Muhammad (Peace be upon Him).
According to many Muslim sources, its exact Date is uncertain but it was one of the Odd-Numbered (21st, 23rd, 25th, 27th or 29th) Nights of the last 10 Days of Ramadan.
Muslims believe that the Night of Qadr comes with Blessings and Mercy of God in abundance, sins are forgiven, supplications are accepted, and that the Annual Decree is revealed to the Angels who carry it out according to God's Grace.
IMPORTANCE
The Reward of acts of Worship done in this one single Night is more than the Reward of a 1000 Months of Worship.
“Indeed, it is We Who sent this Quran down on the Night of Decree: And what will make you realize what the Night of Decree is? The Night of Decree is better than a 1000 Months. The Angels and the Spirit descend therein by permission of their Lord for every matter. Peace it is until the emergence of Dawn.” [Quran-97]
“Whoever spends the Night of Laylat-ul-Qadr in Prayer out of faith and in the hope of Reward, his previous sins will be forgiven.” [Sunan an-Nasai]
THINGS TO DO ON LAYLAT-UL-QADR
1. Offer Duas
During the Holy Night of Laylat-ul-Qadr, Allah is Merciful, and all the sincere supplications are accepted by Him.
2. Recite Quran
Another thing to do on Laylat-ul-Qadr is to recite chapters from the Holy Quran with the translations and contemplating their explanation will cleanse previous sins.
3. Giving Sadaqah
According to Islamic sources, the reward of giving Sadaqah during the Month of Ramadan gets multiplied by 70 times. It is also said that the reward of a good deed during this special night is the same as performing it continuously over 83 years.
4. Perform Itikaf
On this Holy Night, performing Itikaf (seclusion in Masjid) will earn you great Rewards.
5. Do Dhikr
6. Do Istighfar
LAYLAT-UL-QADR DUA
"Allahumma innaka afuwwun tu hibul afwa fa fu anni"
(O Allah, indeed You are Pardoning, You love pardon, so pardon Me)
https://sites.google.com/site/activeislamicinfo/laylat-ul-qadr