This is the Hindu symbol for good Karma which is the cosmic principle according to which each person is rewarded or punished in one incarnation according to that person's deeds in the previous incarnation.
Aum is a universal mantra fit for all people and one not need the initiation of a master or guru to reap it's endless benefits. It must be understood that Aum is the underlying current permeating the universe, is prior to the gunas, the senses, the material world thus the mind and religious affiliation.
"If you watch the way you use speech in your own life, you will notice that most of your speech takes you out of the present moment into the past or future… Words are often used as fences to keep us from being with one another." — Swami Ajaya
Om - This is a Hindu symbol and it represents the three gods Brahma, Vishnu and Maheswara. It is also the meditation symbol. It will increase breathing capacity and clean the respiratory system. If it is chanted in a particular manner, it will increase the concentration and leads to good health.