What does the Om or Aum symbol Mean:

Om or Aum is of paramount importance in Hinduism. This symbol is a sacred syllable representing Brahman,  the impersonal Absolute of Hinduism — omnipotent, omnipresent, and the source of all manifest existence. Brahman, in itself, is incomprehensible; so a symbol becomes mandatory to help us realize the Unknowable.

Om, therefore, represents both the unmanifest (nirguna) and manifest (saguna) aspects of God. That is why it is called pranava, to mean that it pervades life and runs through our prana or breath.

The meaning of the Om chant:

OM, like Amen and Ahmeen means the Divine which manifests as all that is. OM is the “word” as in; “in the beginning was the word” which means primal sound or vibration from which all other names and forms arise and to which we all return. OM is the Alpha and the Omega.