Ashtanga Yoga literally means “eight limbs of yoga.” These limbs are defined in the the second chapter of the Yoga Sutras of Patanjali, and comprise the foundation of Ashtanga Yoga Philosophy.
Asana is the 3rd limb of the 8 limbs, however today, when many people say "Ashtanga" they are often simply referring to Asana, which is the physical sequence of postures as taught by Sri. K Pattabhi Jois.
The following are the 8 practices or limbs:
1. yama (moral restraints) – how we relate to others
2. niyama (observances) – how we relate to ourselves
3. āsana (posture) – how we relate to our body
4. prāṇāyāma (breath extension) – how we relate to our breath or spirit
5. pratyāhāra (sensory withdrawal) – how we relate to our sense organs
6. dhāraṇā (concentration) – how we relate to our mind
7. dhyāna (meditation) – moving beyond the mind
8. samādhi (meditative absorption) – deep realization and inner union