I'll start by answering the last question first.
What is the role of Uthman (may Allah be pleased with him) exactly concerning these readings?
Quran has been transmitted through the time by oral memorization and recitation on a hand of Scholar not through a book. To understand this, we have to understand the definitions.
Quran (القران): is the word of Allah that is recited verbally in any of the authentic readings. "Way of Reading - Qar'ah (plural: Qira't)". Please note that all the readings existed at the time of the prophet and the arc angel Jibreel (AS) taught prophet Mohamed all the authentic methods. The Quran was collected and recited in oral form in the last Ramadan of the prophet death. Arc angel Jibrel (AS) came to the prophet and made him recite the Quran twice in the last Ramadan of the prohet's liefe. As a proof for this claim, the Hadith of Omar (RA):
I heard Hisham bin Hakim bin Hizam reciting Surat-al-Furqan in a way different to that of mine. Allah's Messenger (ﷺ) had taught it to me (in a different way). So, I was about to quarrel with him (during the prayer) but I waited till he finished, then I tied his garment round his neck and seized him by it and brought him to Allah's Messenger (ﷺ) and said, "I have heard him reciting Surat-al-Furqan in a way different to the way you taught it to me." The Prophet (ﷺ) ordered me to release him and asked Hisham to recite it. When he recited it, Allah s Apostle said, "It was revealed in this way." He then asked me to recite it. When I recited it, he said, "It was revealed in this way. The Qur'an has been revealed in seven different ways, so recite it in the way that is easier for you."
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَبْدٍ الْقَارِيِّ، أَنَّهُ قَالَ سَمِعْتُ عُمَرَ بْنَ الْخَطَّابِ ـ رضى الله عنه ـ يَقُولُ سَمِعْتُ هِشَامَ بْنَ حَكِيمِ بْنِ حِزَامٍ، يَقْرَأُ سُورَةَ الْفُرْقَانِ عَلَى غَيْرِ مَا أَقْرَؤُهَا، وَكَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم أَقْرَأَنِيهَا، وَكِدْتُ أَنْ أَعْجَلَ عَلَيْهِ، ثُمَّ أَمْهَلْتُهُ حَتَّى انْصَرَفَ، ثُمَّ لَبَّبْتُهُ بِرِدَائِهِ فَجِئْتُ بِهِ رَسُولَ اللَّهِ صلى الله عليه وسلم فَقُلْتُ إِنِّي سَمِعْتُ هَذَا يَقْرَأُ عَلَى غَيْرِ مَا أَقْرَأْتَنِيهَا، فَقَالَ لِي " أَرْسِلْهُ ". ثُمَّ قَالَ لَهُ " اقْرَأْ ". فَقَرَأَ. قَالَ " هَكَذَا أُنْزِلَتْ ". ثُمَّ قَالَ لِي " اقْرَأْ ". فَقَرَأْتُ فَقَالَ " هَكَذَا أُنْزِلَتْ. إِنَّ الْقُرْآنَ أُنْزِلَ عَلَى سَبْعَةِ أَحْرُفٍ فَاقْرَءُوا مِنْهُ مَا تَيَسَّرَ ".
And the other Hadith:
Gabriel used to repeat the recitation of the Qur'an with the Prophet (ﷺ) once a year, but he repeated it twice with him in the year he died. The Prophet (ﷺ) used to stay in Itikaf for ten days every year (in the month of Ramadan), but in the year of his death, he stayed in I
tikaf for twenty days.
حَدَّثَنَا خَالِدُ بْنُ يَزِيدَ، حَدَّثَنَا أَبُو بَكْرٍ، عَنْ أَبِي حَصِينٍ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ كَانَ يَعْرِضُ عَلَى النَّبِيِّ صلى الله عليه وسلم الْقُرْآنَ كُلَّ عَامٍ مَرَّةً، فَعَرَضَ عَلَيْهِ مَرَّتَيْنِ فِي الْعَامِ الَّذِي قُبِضَ، وَكَانَ يَعْتَكِفُ كُلَّ عَامٍ عَشْرًا فَاعْتَكَفَ عِشْرِينَ فِي الْعَامِ الَّذِي قُبِضَ {فِيهِ}
Mushaf (المصحف): is the written form of the Quran or the book. Uthman (RA) ordered the collection for the 2nd time of the know Quran into a book to maintain the knowledge in written format as well. And to help those from non Arab origins, who joined Islam recently, to be able to read and learn. The reason he burnt all the other sources is to maintain a revised and authentic version of the Mushaf. Please note that first time the Quran was collected in written format was at the time of Abu Bakr (First Caliph). The difference between the 2 version is the quality of the writing and the materials used for the book but the content was the same as they were collected by the same person (Zaid Ibn Thabet). I could go into details of the process Zaid had followed to authenticate the collection of each verse in the Quran but this is irrelevant to this question. The reason Abu Bakr ordered the collection of the Mushaf is that there is a large number of the holder (memorizers) of the Quran whom had martyred in the battle of Yamamah and Abu Bakr was worried that he might Quran by lost with the death of the memorizers.
The Mushaf that was collected by Uthman incorporated all the readings of the Quran. Please note that this Mushaf didn't have dots that are present in the current Arabic language letters. And that how the Arabic letters were written at that time. You might ask how would they know how to differentiate between the words? The answer it was kind of understanding that an arab would right away spot the word and understand the actual mapping. Dots were introduced latter in the time of Aummiat's Caliphate because the people of non-arab background didn't recognize the writing.
What does a reading of Quran means? Does that mean we have different versions of the Quran?
Reading of Quran: is a set of rules that guides the reader on how he or she could pronounce the Quran which includes the how use your mouth, tounge extensive to generate a specific sound.
There are very few differences in words between some of the readings of the Quran based on Uthman's Mushaf. This difference come from the location of the dot like the letters: ج, ح, خ
As you see the above letters, the only difference is the location of the dot. Educated Arab back then was able to recognize the word even if it didn't have those dots.
The differences could be in 1 or 2 letters used in conjecture like "and: و ", etc...
But again those differences are minimal and they are known for a person who studies the readings of the Quran and none changes the meaning of the Quran by all means. It either strengthen the meaning or just a difference in pronunciation.
What is an authentic reading of the Quran?
Scholars agreed that an authentic narration is a narration that has a strong chain or chains of known narrators from the narrator till prophet Mohamed (PBUH). These chains of narrations still exist till today for all the different readings of the Quran. The shorter the chain between the scholar till the prophet the stronger the narration. Today there is a person who have 27 or 26 narrators between him and the prophet. And that scholar lives in Egypt currently.
How the oral transmission works?
To become a narrator, you have to be permitted "تجاز" or get an a permission of narration. To get that permission, you need to stay with scholar for a time in which you recite the whole Quran from Memory with correct pronunciation of each letter. Usually, the stronger the narrator "shorter chain", the tougher he is to give you that "permission". Because by giving you that permission, he gives you the allowance to transmit that knowledge. And you become one of the holders of the Quran. And this is a major task. It would take some people about 3 to 6 years with a Scholar to get that permission for one reading. The toughest is the first reading, once you get that it would becomes easier for the rest of the readings as there not to much differences. All you need to understand the differences and the difference in pronunciation. Please note that you get a permission per reading. Each reading require another permission.
What are the known Qirat? How many are they? And why they are named that way?
At the time of the prophet, usually each companion kind of memorized the Quran using one of those Qirat. Once those companions started to teach the new comers to Islam, 10 major scholars became known and each with different reading based on whom from the companions and the followers of the companions taught them. Those scholars are:
- Assem (عاصم)
- Abu Amr elbasery (ِابو عمرو البصري)
- Nafia (نافع)
- Ibn Kathir (ابن كثير)
- Hamza (حمزة)
- ElKasaai (الكسائي)
- Ibn Ammer (ابن عامر)
- Abu Jaffar (ِابو جعفر)
- Yaqub (يعقوب)
- Khalaf (خلف)
After each of the major scholars mentioned above, each have 2 major students who became popular. The most popular reading in the muslim world right now is one called:
Hafs from Assem (حفص عن عاصم) which means, the major student "Hafs" recited on Assem and he became a scholar him self.
There are 4 other readings which doesn't have a continuous chain of narrations, so scholars study them for completion. It's forbidden to pray with those 4. I was not able to get the names for those ones. Which makes the total 14 readings. But usually, people refer to the major 10 listed above.
Now, you might hear that they are only 7 (dropping the last 3 in the list above). The reason why, at the beginning of the Muslim conquest the 7 major scholars and their students stayed in a certain area while the other 3 were spread in a different area of the world until a scholar by the name of "Ibn el Jazerry (بن الجزري)" came and traveled through out the world and he found about the other 3 readings. He collected the 3 with 7 known make them 10 including the 2 major students of each which makes the total 20. As I mentioned there are 4 other readings are not authentic (not mentioned in the list above). "القرأت الشاذة"
References:
- https://ar.wikipedia.org/wiki
- https://ar.wikipedia.org/wiki (2)
- https://ar.wikipedia.org/wiki (3)