Let us understand what OM is
. OM comprises of three Sanskrit alphabets Ah, U, Ma and a bindu. It is called Ahkara, Ukara Makara Bindu samyuktham
i.e. OM is made up of these three letters with a dot above Ma, which is called bindhu. We should pronounce OM beginning from our naval area which is called muladhara chakra. So Ah starts from the naval chakra. U should be joined with Ah at heart chakra or anahat chakra. Ma should be joined with Ah and U at the mouth which is called vishudhi chakra. Bindu should be joined in the area of eye brows or ajna chakra. At ajna chakra OM takes its complete form and from here it moves to the top of the head or crown chakra and merges with akash or ether. From ajna chakra to the crown chakra there are a number of chakras in between, which we will discuss later during kundalini meditation
. OM has been referred as Brahman by various Upanishads. In Katha Upanishad
Yama, the God of death says that OM is indestructible Brahman.
Yama also says that OM is both with attributes and without attributes (prakasha and vimarsha). Chandogya Upanishad says that OM is uthgitam. Uthghitam means chanting aloud. When a singer sings it is called uthghitam. This Upanishad also says that OM is paramatman or the universal consciousness. Nasikyam pranam udgitam upasancakrire says Chandogya, which means that OM is worshiped by Gods as the vital force in the nose. This is the reason that third eye or ajna chakra is given great importance. Om ithi Brahma, Om ithi sarvam says Taittiriya Upanishad. OM is Brahman and OM is everything says this Upanishad. It also says that OM implies assent. This is the reason why all mantras begin with OM. Mandukya Upanishad begins with OM iti etat aksharam idam sarvam meaning OM is everything. This Upanishad further says that OM being everything, it is past, present and future. If something can be conceived beyond OM it can only be OM. We have so far seen that OM or Omkara is indestructible Brahman, it is worshipped by even Gods and OM does not have time concept and it is everything. There is nothing beyond OM. The OM meditation lays a strong foundation towards self realization.