"Like many other mantras this one starts with the word "Om." It is considered that Om is the the original sound, the sound of the Universe of which all sounds come from. We can see it as an equivalent to the white light, in which it can be found all the colors of the rainbow. In the Hindu tradition Om is word of solemn affirmation and respectful agreement.
The second part of the mantra, Shanti, means "Peace," that simple. It is a beautiful meaning and also a beautiful sound. This is interpreted as peace in the body, speech and mind (our whole being) or as a desire for peace individually, collectively and universally.
"Om Shanti Om" it is one of the Vedic Mantra which has got religious and philosophical meaning. Om is believed to be a sound of the whole cosmic manifestation. And Shanti is the "Peace". It means 'Om Shanti' means peace for the all human kind, peace for all living and non living beings, peace for the universe, peace for each and every things in this whole cosmic manifestation. Hindus not only pray for their group or for themselves, they pray for every one and every thing and that is what Vedas teach us to do.