The Qur-an is the final version of the same Message that Allah (God) had sent earlier to mankind through many of His Rusul (Messengers).
The Holy Qur-an is the source of all Islamic religious beliefs and practices. It is the most read and the most quoted book in the world. This is the only Book, which has been memorized by millions of people by heart since its revelation. 
The Qur-an was revealed in small portions over a period of 23 years. There are 114 Chapters in the Qur-an. Each chapter of Qur-an is called a Surah. Each Surah (Chapter) is divided into various Ayat (Verses). Some Suwar (Chapters-Plural of Surah) contain more verses while others less. Surah al-Baqarah, the second chapter of the Qur-an, is the biggest of all. It contains 286 Ayat (Verses). The shortest Surah of the Qur-an is
Surah al-Kauthar (A river in Paradise). It contains only three Ayat (Verses). Though there are other Suwar (Chapters-Plural of Surah) that also contain only three Ayat (Verses) but they contain more words and lengthy sentences. The other Suwar (Chapters-Plural of Surah) which contain only three Ayat (Verses) are Surah al-‘Asr (The Time) and Surah an-Nasr (The Help).

The Qur-an is also divided into thirty almost equal portions. Each of these portions is called a Juz in Arabic.

The Qur-an was revealed to the Messenger of Allah, Muhammad صلى الله عليه وسلم in small portions. Some portions of the Qur-an were revealed in Makkah while other portions of it were revealed in Madinah. The Suwar (Chapters) that were revealed in Makkah, are known as Makki Suwar. TheSuwar (Chapters) revealed in Madinah after Hijrah (Migration), are known as Madani Suwar.  

The Makkan period of revelation was from 610 AD to 622 CE. The Madani period was from 622 CE to 632 CE. Eighty-six (86) Suwar (Chapters) were revealed in Makkah, and twenty-eight (28) Suwar (Chapters) were revealed in Madinah.

Makki Suwar contain 4417 Ayat (Verses), Madani Suwar contain 1819 Ayat
(Verses).
The total number ofAyat (Verses) in the Hoy Qur-an is six thousand two hundred thirty six (6,236).

The Messenger of Allah, Muhammad صلى الله عليه وسلم received the first Wahi (Message from Allah) in 610 CE, in the small cave in the mountain of Hira. That mountain is now known as Jabl Nur (Mountain of Radiance). It is located about two and a half miles (Four Kilometers) away from the Ka’bah in the city of Makkah.

In the first Wahi (Message from Allah), the Messenger of Allah, Muhammad صلى الله عليه وسلم received the following first five Ayat (Verses) of Surah (Chapter) al-‘Alaq (The Clot).

The last revelation of the Qur-an was the two hundred eighty-first Ayah (Verse) of
Surah (Chapter) al-Baqarah (The Cow).

Surah al-Fatihah (The Opening Chapter), the first Surah (Chapter) of the Qur-an was the first complete chapter to be revealed and Surah an-Nasr (The Help) was the last.

When the Qur-an was being revealed, the Messenger of Allah, Muhammad صلى الله عليه وسلم used to recite the revealed verses to his Sahabah (Companions). They used to learn these verses by heart. Some of the companions used to write them on palm leaves, animal hides, stone tablets and any other available media. The Suwar (Chapters) and
Ayat (Verses) of the Qur-an are not arranged in their chronological order of revelation. The Messenger of Allah, Muhammad صلى الله عليه وسلم used to set the place of various Suwar (Chapters) and Ayat (Verses) himself.

There were several designated Katib Al-Wahi (Writer of Messages from Allah) who used to write down the divine revelations whenever the Messenger of Allah, Muhammadصلىاللهعليهوسلم received them.

After the demise of the Messenger of Allah, Muhammad صلى الله عليه وسلم , many newly converted tribes revolted. Most of them decided to follow most principles of Islam, except the institution of Zakah (Poor Due Charity). One cannot pick and choose beliefs in Islam. There is no compromise with the basic Islamic beliefs.

Abu Bakr رضي الله عنه, a prominent Sahabi (Companion of Muhammad صلى الله عليه وسلم) became the first Khalifah (Caliph) of Muslims. Soon after assuming this responsibility, he had to face severe challenges in the form of several revolts. He also had to face challenges from several claims of false Prophethood from several apostates. He decided to firmly deal with them. He sent Muslim armies to suppress the rebellion. As a result, many of those Huffaz (Those who had memorized Qur-an by heart) died.

‘Umar bin Khattab رضي الله عنه, another prominent Sahabi (Companion of Muhammad S) pondered upon the situation. He felt an urgent need to compile the scattered portions of the Qur-an into one volume. He suggested it to Abu Bakr رضي الله عنه, who was initially reluctant to undertake such a task. His reasoning was that since the Messenger of Allah, Muhammad صلى الله عليه وسلم did not make any such compilation during his lifetime, so how could he? But after thinking over the matter, he agreed to ‘Umar bin Khattab رضي الله عنه’s suggestion. Subsequently, a committee was set up for compiling the Qur-an. It was headed by Zayd bin Thabit رضي الله عنه, the secretary of the Messenger of Allah, Muhammad صلى الله عليه وسلم, who also was the main Katib Wahi (Writer of Messages from Allah). This team compiled the Holy Qur-an in one volume. This copy of the Qur-an was verified by all Sahabah (Companions of Muhammad صلى الله عليه وسلم) who used to memorize each Ayah (Verse) and Surah (Chapter) of the Qur-an as it was revealed to the Messenger of Allah, Muhammad صلى الله عليه وسلم.

This copy of the Qur-an was kept in the custody of Hafsah bint ‘Umar رضى الله عنها, a widow of the Messenger of Allah, Muhammad صلى الله عليه وسلم. After Abu Bakr, ‘Umar bin Khattab رضي الله عنه became the second Khalifah (Caliph) of Muslims, but he, for some reason, did not publish the compiled version of the Qur-an.

It was during the tenure of the third Khalifah (Caliph) of Muslims, ‘Uthman bin ‘Affan رضي الله عنه, a standardized version of the Qur-an was made from the available document and its copies were sent to all other towns and cities.
The Qur-an which we read today is the exact copy of the one published by the third
Khalifah (Caliph) of Muslims, ‘Uthman bin ‘Affan رضي الله عنه.  

There are three main themes of the Qur-an, Wahdah (Oneness of Allah), Risalah
(Allah‘s Messengers and the finality of Messengers) and Akhirah (Day of Judgment and life after death).

The main emphasis of the Qur-an is Tawhid i.e. the Oneness of God, and the finality of the Messengership of Allah, Muhammad صلى الله عليه وسلم. Besides, it contains the stories of previous Messengers, moral teachings and the injunctions of Shari’ah. It also informs us about other revealed books, about angels, about the Last Day of Judgment and Paradise and Hell.

The Qur-an is the most comprehensive book of law. It deals with each and every aspect of human life. Its rules are easy and simple. It does not unnecessarily stress mankind. It does not lead to asceticism. It clearly states:

S: Sallallahu 'Alayhi Wasallam
R: Radiallahu Anhu