In order to prove a theory, all the facts must fit, there should be no inconsistencies. Brother Bkanwar has given us a new understanding of the letters at the start of Surah 2 which has been challenged by some of our learned colleagues. The proper response from Brother Bkanwar is to come up with a similar understanding for ALL the remaining letters at the beginning of all the chapters that have them. Does his ALM explanationfor surah 2 fit every chapter (surah 3, 29 etc) that these letters start with? The same explanation should fit these chapters, should they not? If he can do this, then the critics would be silenced, big time!
The complete Muqatta'at letters and their appearance in the Quran
Chapter 2, The Cow: Alif Laam Mim
Chapter 3, Ale-Imran: Alif Laam Mim
Chapter 7, al-A’araaf: Alif Laam Mim Suad
Chapter 10, Yunus: Alif Laam Ra
Chapter 11, Hud: Alif Laam Ra
Chapter 12, Yusuf: Alif Laam Ra
Chapter 13, Ra'd: Alif Laam Mim Ra
Chapter 14, Ibrahim: Alif Laam Ra
Chapter 15, Hijr: Alif Laam Ra
Chapter 19, Maryam: Kaf Ha Ya Ain Suad
Chapter 20, Ta-Ha: Ta Ha
Chapter 26, The Poets: Ta Sin Mim
Chapter 27, The Ant: Ta Sin
Chapter 28, Qasas: Ta Sin Mim
Chapter 29, The Spider: Alif Laam Mim
Chapter 30, The Romans: Alif Laam Mim
Chapter 31, Luqman: Alif Laam Mim
Chapter 32, The Adoration: Alif Laam Mim
Chapter 36, Ya-Sin: Ya Sin
Chapter 38, Suad: Suad
Chapter 40, The Believer: Ha Mim
Chapter 41, Fussilat: Ha Mim
Chapter 42, Shuraa: Ha Mim; Ain Sin Qaf
Chapter 43, The Embelishment: Ha Mim
Chapter 44, The Smoke: Ha Mim
Chapter 45, The Kneeling: Ha Mim
Chapter 46, The Sandhills: Ha Mim
Chapter 50, Qaf: Qaf
Chapter 68, The Pen: Nun
Dr Shabir has a different explanation, for example:-
2:1 A.L.M. Alif-Laam-Meem. (Allah, Lateef the Unfathomable, Majeed the Magnificent, knows and understands your needs.)
19:1 K.H.Y.'A.S. Kaaf Ha Ya ‘Ain Saad (Kareem the Honored, Haadi the Guide, Yaamen the Bounteous, ‘Aleem the Knower, Saadiq the True, states that)
42:2 'A.S.Q. ‘Ain-Seen-Qaaf. (‘Aleem the Knower, Samee' the Hearer, Qaadir the Almighty, proclaims that),
Of the 28 letters of the Arabic alphabet, exactly one half appear as muqattaat, either singly or in combinations of two, three, four or five letters.The fourteen letters are: أ ح ر س ص ط ع ق ك ل م ن ه ي (alif, ha, ra, sin, sad, ta, ain, qaf, kaf, lam, mim, nun, ha, ya).
Certain co-occurrence restrictions are observable in these letters; for instance, alif is invariably followed by lam. The substantial majority of the combinations begin either alif lam or ha mim.
In all but 3 of the 29 cases, these letters are almost immediately followed by mention of the Qur'anic revelation itself (the exceptions are suras 29, 30, and 68); and some argue that even these three cases should be included, since mention of the revelation is made later on in the sura. More specifically, one may note that in 8 cases the following verse begins "These are the signs...", and in another 5 it begins "The Revelation..."; another 3 begin "By the Qur'an...", and another 2 "By the Book..." Additionally, all but 3 of these suras are Meccan suras (the exceptions are suras 2, 3, 13.)
The suras that contain these letters are: sura 2, sura 3, sura 7, sura 10, sura 11, sura 12, sura 13, sura 14, sura 15, sura 19, sura 20, sura 26, sura 27, sura 28, sura 29, sura 30, sura 31, sura 32, sura 36, sura 38, sura 40, sura 41, sura 42, sura 43, sura 44, sura 45, sura 46, sura 50, sura 68.
Laam and Meem are conjoined and both are written with prolongation sign/Mark. One letter is written in two styles. [Refer 19:01 and 20:01] Letter 20:01 is used only in the beginning and middle of a word and that in 19:01 is not used as such. الم is also the First Ayah of Sura 3, 29, 30, 31 and 32 [total 6].
Tomes have been written over the centuries on the possible meanings and probable significance of these 'mystical letters' as they are sometimes called. Opinions have been numerous but a consensus elusive. There is no reliable report of Muhammad having used such expressions in his ordinary speech, or his having thrown light on its usage in the Qur'an. And, more importantly, none of his Companions seemed to have asked him about it. This apparent lack of inquisitiveness is cited as proof that such abbreviations were well known to the Arabs of the time and were in vogue long before the advent of Islam.
One well-known opinion is that these letters stand for words or phrases related to God and His Attributes. The famous Companions Ibn Abbas and Ibn Mas'ud are said to have favored this view, as cited by Abu Hayyan al Andalusi in his Bahr Al Muhit. As plausible as it may sound, this opinion does not find favor among other classical commentators, because the possible combinations of letters are virtually infinite and the Attributes they represent seem to be chosen arbitrarily.
Fakhr al-Din al-Razi, a classical commentator of Quran, has noted some twenty opinions regarding these letters, and mentions multiple opinions that these letters present the names of the Surahs as appointed by God. In addition, he mentions that Arabs would name things after such letters (for example, 'money' as 'ع', clouds as 'غ', and fish as 'ن'). 
Amin Ahsan Islahi, a renowned exegete of the Quran, has mentioned that since Arabs once used such letters in their poetry, it was only appropriate for Quran to use that same style. He agrees with Razi and mentions that since these letters are names for Surahs, they are proper nouns. As such, they do not necessarily refer to other matters. At the same time, he cites research from Hamiduddin Farahi, a Quranic scholar from the Indian subcontinent, on how these letters must be appropriately chosen according to the content and theme of the surahs. Farahi links these letters back to Hebrew alphabet and suggests that those letters not only represented phonetic sounds but also had symbolic meanings, and Quran perhaps uses the same meanings when choosing the letters for surahs. For instance, in support of his opinion, he presents the letter Nun (ن), which symbolizes fish and Surah Nun mentions Prophet Jonah as 'companion of the fish'. Similarly, the letter Ta or Tuay (ط) represents a serpent and all the Surahs that begin with this letter mention the story of Prophet Moses and serpents.
Western scholars have only occasionally attempted to explain them. In 1996, Keith Massey proposed new evidence for an older theory that the "Mystery Letters" were the initials or monograms of the scribes who originally transcribed the suras . As evidence for this, he demonstrated that the letters themselves occur in a specific order, suggesting a hierarchy of importance. This idea has not yet gained wide acceptance. Other explanations have similarly failed to satisfactorily explain the letters.