'AUM' the all-encompassing cosmic vibration of the universe
The Sanskrit is praNava, meaning ever new.
We often chant this in yoga class but have you ever wondered what AUM means?
This mantra is a commonly used one in our practice to unite the energy of the class, as well as a natural extension of the mantra,
According to the Mandukya Upanishad, the syllables of AUM represent the following realms of experience:
AUM can be broken into five sacred parts.
A, represents creation and begins within the navel.
U, represents preservation and is held within the lungs.
M, represents destruction and is released through the throat. 
Furthermore, the syllables of AUM also symbolize the three principles of existence:
we engage the essence of A, Brahma the Creator, U, Vishnu the Preserver and M, Shiva the Destroyer during these three stages. 
A also symbolizes the conscious, waking state.
U symbolizes the dream state
M represents the dreamless sleep of mind and spirit.
When we look at the symbol in its entirety, with the crescent and the dot, it represents the combination and transition of all those states, the state of ‘samadhi’ merging with the universal consciousness. 
These three letters symbolize many other aspects and there is no denying the importance of AUM in helping us focus our mind, body, and practice into a sacred act.
aum, Yoga, and the 3 gunas
According to yoga the human body and mind are made up of three gunas, which make up our 'nature' or 'tendencies' of Prakṛti (found within both the macrocosm and microcosm).
AUM symbolizes the three gunas as:
A - rajas - passion, change, activity birth, and dynamism,
U - sattva - harmony, clarity, contemplation, faith, existence, reality, and lightness,
M - tamas - ignorance, darkness, death, passivity, and inertia.
There is also the sacred space before and after the chant.
The silence which symbolizes the transcendence of all the three gunas – trigunatita - pure consciousness.
The whole symbol representing Brahman, the perfect state.
The silence that is present represents the underlying reality which underlies and is beyond that which is created, sustained and destroyed.
The whole universe is created from “Aum.” Vibrating “Aum” helps to align our energy to the universal energy, clearing our mind and connecting us to the whole. It engages all the components of the larynx/mouth and the entire spectrum of human sound. It becomes a meditation upon itself and when applied with intention connects us to the universal song.
Another way to begin and seal your practice and each sacred day.