As for the meaning of the disjointed letters in the Qur’an, there are different views as follows: Abu Bakr (may Allah be pleased with him) said: “In every divinely-revealed book there is a divine secret; in the Qur’an, it is these letters.” Ibn `Abbas was reported to have said that these letters stand as a proof of the authenticity of the words that occur after them. In Az-Zamakhshari’s Kashshaaf, we read: “These letters indirectly denote that though being part of their own language, the Quraysh tribe failed to produce the like of the Qur’an.” Some scholars adopt the view that these letters are names of the surahs (chapters of the Qur’an) in which they are mentioned.

In another place, we find that these letters are an aspect of the challenge directed to the disbelievers (to produce the like of the Qur’an). Although the Prophet (peace and blessings be upon him) was illiterate, he brought something very unique in every aspect.
The eminent Muslim scholar, Dr. `Abdul-Fattah `Ashoor, Professor of the Exegesis of the Qur’an at Al-Azhar Univ, states: “Alif Lam Mim” [and the like] are separate or disjointed letters that many Qur’anic surahs start with.
Scholars hold different opinions regarding their meaning. The most correct opinion is that Allah refers to the fact that the Qur’an consists of the like of these letters. The People of Quraysh were challenged to produce the like of the Qur’an, which is of Arabic letters, and they failed to produce its like. They failed to produce 10 surahs, a single surah, or even a verse.
This sheds light on the fact that the Qur’an is revealed by Allah. No one can produce it, even the Prophet himself who was an eloquent man.
Allah Almighty says: “Say: Verily, though mankind and the Jinn should assemble to produce the like of this Quran, they could not produce the like thereof though they were helpers one of another.” (Al-Isra’: 88)