The night journey and ascent
of the Prophet Muhammad, and the revelation
of Salat.
The festival is celebrated
by telling the story of how the Prophet Muhammad
was visited by two archangels while he was asleep, who purified
his heart and filled him with knowledge and faith.
The Prophet travelled from
Mecca to Jerusalem in a single
night on a strange winged creature called Buraq. From
Jerusalem he ascended into heaven, where he met the earlier
prophets, and eventually God.
During his time in heaven Muhammad
was told of the duty of Muslims to recite Salat
(ritual prayer) five times a day.

Al-Buraq
seen on a reproduction of a 17th century Indian Mughal
miniature
"The story of Lailat
al Miraj consists of two major parts. The first part of the
story begins with the Prophet Muhammad at
the Kabaa in Mecca. He is visited by two archangels who provide
him with a mythical winged steed called Buraq.
Buraq carries the Prophet to the 'Farthest Mosque,' believed
by Muslims to be the Al Aqsa mosque in Jerusalem,
where Muhammad joins past prophets in prayer.
The Prophet then ascends
to heaven where he is told by God of the duty for Muslims
to pray five times daily (Salat). This second part
of the journey is commonly referred to as the Miraj,
an Arabic word meaning "ladder."
The events of Lailat al
Miraj are described briefly in chapter 17 of the Quran, which
is named "Sura Al-Isra" after the Prophet's ascension
to heaven. Many of the details of the story are filled in
by hadith, supplemental writings about the life of the Prophet
Muhammad.
Today Lailat al Miraj
is observed by Muslims as one of the most important events
in the history of Islam. Muslims may attend special prayer
services at a mosque, or they may commemorate the holiday
privately at home by telling the story to children or reciting
special nighttime prayers."
http://www.huffingtonpost.com/2011/06/28/lailat-al-miraj_n_885922.html