This is a flow sequence from the Ashtanga discipline that serves to warm the body and connect breath and movement. It is generally practiced before deeper yoga asanas or at the beginning of practice.
Surya Namaskar is a devotional offering to the sun which awakens the chakras within the body and creates an opening so that we may embody the symbolic heat and light that the sun generously provides, to support us as we still the mind through our asana practice, for meditation.