" Om, Aum, Ohm is a holy meditation symbol of Hinduism, Buddhism, and Jainism with a profusion of esoteric and exoteric meanings. In modern usage Om means the Word, the parnava, the eternal. Various accounts are given of its origin; one that it is the term of assent used by the gods, and probably an old contracted form of the Sanskirt word "evam" meaning "thus." The laws of the "Manu" say that the word was formed by Brahma himself, who extracted the letters "a" "u" "m" from the "Vedas," one from each; and they thus explain its mysterious power and sanctity. "Om" is also the name given by the Hindus to the spiritual sun, as opposed to "Sooruj," the natural sun.
The word is Sanskrit. It is pronounced at the beginning and end of every lesson in the "Veda" and it is also the introductory word of the "Puranas." It is said in the "Katha-Upanishad": "Whoever knows this syllable obtains whatever he wishes." This is because all words are said to be but various forms of the one sound, "om", according to the Upanishads." It represents the divine and the power of God. It is the sound-symbol for the ultimate reality."
It is Hinduism, not Islam. I know it is used in meditation, but to realize what ever you want you need to attain enlightenment first than chant any good name of God, OHM if you want but not necessarily, you've got to get in tune with God from inside out of yourself, otherwise you can chant whatever you want, if you are not CLEAN and highly educated, you will be wasting your time, If you do not believe me, you can ask people with 20 and more years of Hindu meditation with no avail.