Yoga Ashtanga Flow
Yoga's philosophy is based on eight limbs; only one of them, asana, is about the poses. The rest: yama, niyama, pranayama, pratyahara, dharana, dhyana and samadhi, are best described as moral and ethical codes to live by.
These codes are intended to help people live meaningful and purposeful lives; to have compassion, and not be ruled by the ego and mostly useless thoughts that can control our lives if we let them.
But many of us do yoga because of its physical benefits, improved strength and balance, as well as greater flexibility (which can make everyday activities easier on your body).