The “sun” symbolizes a subtle conduct (Pingala), located to the right of the vertebral axis, which corresponds to the energetic aspect of our personality.
The other sense of the concept “sun” is the Muladhara Chakra, an intense energetic center located above the ombillic.
To the left of the vertebral axis is Ida, an other subtle conduct whose symbol is the moon (Tha), which corresponds to the hidden, mysterious, quiet side of our personality.
The “moon” can also symbolize the Ajna Chakra, the energetic center located between the eyebrows.
Concerning the word “Yoga“, it comes from the Sanskrit root “Yuj” which means “unite together” and gave the english word “yoke”.
So … What are the aspects that must be united?
First, the purpose is to make, within our own body, the union of opposing principles such as in couples attachment/repulsion, excitement/relief, euphoria/depression, passionate love/hate, etc. to achieve a state of calm and inner strength.
Then, the union sought is that of the body with the mind, that must walk “hand in hand”, as friends.
On a subtle plane, the aim is to unite the male and female aspects of our personality (Pingala and Ida).
Finally, the ultimate goal of yoga is the union of the individual self (Jiva), which corresponds to the ego, with the Absolute (Brahman).
The benefits of Yoga are realized in the body (recreation, relaxation, flexibility, strength) and psychologically (mental calm, developing of the capacity for concentration and memory, and better resistance to stress).
The traditional way of receiving the knowledge of Hatha Yoga is in personal courses.
A feeling of unity of body and mind is felt from the early courses.