Al-Fatihah, is the Opener of the Book, the Surah with which prayers are begun. – It is also called, Umm Al-Kitab (the Mother of the Book), according to the majority of scholars.
In an authentic Hadith recorded by At-Tirmidhi, who graded it Sahih, Abu Hurayrah said that the Messenger of Allah said,
الْحَمْدُ للهِ رَبَ الْعَالَمِينَ أُمُّ الْقُرْآنِ وَأُمُّ الْكِتَابِ وَالسَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ
Al-Hamdu lillahi Rabbil-`Alamin is the Mother of the Qur’an, the Mother of the Book, and the seven repeated Ayat of the Glorious Qur’an. It is also called Al-Hamd and As-Salah, because the Prophet said that his Lord said,
قَسَمْتُ الصَّلَاةَ بَيْنِي وَبَيْنَ عَبْدِي نِصْفَيْنِ، فَإِذَا قَالَ الْعَبْدُ:الْحَمْدُ للهِ رَبِّ الْعَالَمِنَ، قَالَ اللهُ: حَمِدَنِي عَبْدِي
The prayer (i.e., Al-Fatihah) is divided into two halves between Me and My servants. When the servant says, `All praise is due to Allah, the Lord of existence,’ Allah says, ‘My servant has praised Me. Al-Fatihah was called the Salah because reciting it is a condition for the correctness of Salah – the prayer. Al-Fatihah was also called Ash-Shifa’ (the Cure). It is also called Ar-Ruqyah (remedy) since, in the Sahih, there is the narration of Abu Sa`id telling the story of the Companion who used Al-Fatihah as a remedy for the tribal chief who was poisoned.
Later, the Messenger of Allah said to a Companion,
وَمَا يُدْرِيكَ أَنَّهَا رُقْيَةٌ
How did you know that it is a Ruqyah? Al-Fatihah was revealed in Makkah as Ibn Abbas, Qatadah and Abu Al-Aliyah stated. Allah said,
وَلَقَدْ ءاتَيْنَـكَ سَبْعًا مِّنَ الْمَثَانِي
And indeed, We have bestowed upon you the seven Mathani (seven repeatedly recited verses), (i.e. Surah Al-Fatihah) (15:87). Allah knows best.