This is an image of the Om symbol, which is a sacred sound. This symbol is from the Hindu religion. It symbolizes the connection between what is inside the self (the soul, el espiritu), and the universe, or the great unknown, the entirety of the world.
Wikipedia says that "In Hinduism, Om is like calling god's name towards you."
Therefore, the sound of Om is used to bring ourselves into a spiritual state, a closeness to God.