The asana sequence known as Sūrya Namaskār literally means “salute to the sun” (surya = sun, namaskar= salute).
In Hindu mythology, the sun god is worshiped as a symbol of health and immortal life. The Sun Salutation originated as a series of prostrations to the sun. Traditionally, it is performed at dawn, facing the rising sun. In time, each of the twelve positions came to have its own mantra, celebrating aspects of the sun’s divinity.
The Sun Salutation is a graceful sequence of twelve positions performed as one continuous exercise. Each position counteracts the one before, stretching the body in a different way and alternately expanding and contracting the chest to regulate the breathing. Practiced daily it will bring great flexibility to your spine and joints and trim your waist. It limbers up the whole body in preperation for the Asanas (postures).
The sun salutation is ideal for loosening stiff muscles and regaining flexibility. In addition, it stimulates the body’s circulation and promotes deep breathing. The series of motions is conceived to optimally stretch and warm up all muscles. But respiration also plays an important role: stretching and rhythmic breathing together relax the body and eliminate stress and tension.
Reference: Sivananda Yoga